The string "abababab..." of length $$$k + 1$$$ is a $$$k$$$-Fortnite string. Then, set a variable s = "a", and add "a" or "b" to s $$$k$$$ times.

import sys, math, random
input = sys.stdin.readline
out = []
 
for _ in range(int(input())):
    n = int(input())
 
    s = "a"
    for i in range(k):
        if i % 2 == 0:
            s += "b"
        else:
            s += "a"

    out.append(s)
 
print("\n".join(out))

First, sort the array of initial positions $$$a$$$.

Note that if there are two business majors on consecutive squares, Akash cannot get past them. Thus, we can loop through $$$a$$$ and check that no two consecutive elements are consecutive.

If there are no business majors blocking the path, Akash can reach the lactation pod in $$$n - 1$$$ seconds.

If the positions of two consecutive business majors have the same parity, Akash can get by both without pausing. Otherwise, if they have the same parity, Akash must pause one second to ensure he can move past the second business major. Additionally, if the first business major is on an odd square, Akash must wait a second to get past the first business major.

We can keep a variable curParity representing the parity of the last processed business major. Initially, curParity is set to 0, representing the fact that if the first business major is on an odd square, Akash must wait a second. Also, keep a counter pauses to count how many times Akash must pause.

Then, loop through the array $$$a$$$. If the position of the next business major has a different parity than curParity, then increment pauses by $$$1$$$ and update curParity. Otherwise, Akash does not have to pause, and no action needs to be taken.

Then, we can print $$$n - 1$$$ added to the number of pauses.

import sys
input = sys.stdin.readline
out = []
 
for _ in range(int(input())):
    n, m = map(int, input().split())
    A = list(map(int, input().split()))
    A.sort()
 
    for i in range(m - 1):
        if A[i] + 1 == A[i+1]:
            out.append(-1)
            break
    else:
        curPar = 0
        pauses = 0
        for x in A:
            if x % 2 != curPar:
                curPar = x % 2
                pauses += 1
        
        out.append(n - 1 + pauses)
 
print("\n".join(map(str, out)))

Since the limit on $$$n$$$ is quite small, we can afford a solution in $$$O(n^2)$$$. This means we can loop through all possible swaps.

First, let's see how much any given swap adds to the final sum of the heights. Consider swapping $$$a_i$$$ and $$$a_j$$$. Then, after a week, instead of mushrooms with heights $$$ia_i$$$ and $$$ja_j$$$, we get mushrooms of heights $$$ia_j$$$ and $$$ja_i$$$. Thus, the swap contributed

to the final sum.

We can loop through the array and find the two best swaps, by finding the highest and second highest value of $$$(i - j)(a_i - a_j)$$$ over all pairs of indices $$$(i, j)$$$. Let the two best swaps be $$$(i, j)$$$ and $$$(h, k)$$$.

Note that if $$$n = 2$$$, there is only $$$1$$$ possible swap, so we deal with this case separately. Akash's choices are forced, so this should be easy.

If these indices are all distinct, then we just need to perform these two swaps.

Otherwise, the problem is more interesting. WLOG say they share an index, $$$i = h$$$. That is, the two best swaps are $$$(i, j)$$$ and $$$(i, k)$$$. We can be greedy here: the best sequence of swaps will always involve one of these two swaps (reasoning for this given below). Then, we can make each swap, and go through all possible swaps again, and see what combination gives us the best possible increase.

import sys, math
input = sys.stdin.readline
out = []
 
for _ in range(int(input())):
    n = int(input())
    A = list(map(int, input().split()))
    
    if n == 2:
        out.append(A[0] + 2 * A[1])
    else:
        bestScore = -math.inf
        bestPair = (0, 0)
        secBestScore = -math.inf
        secBestPair = (0, 0)
        for i in range(n - 1):
            for j in range(i+1, n):
                score = (A[i] - A[j]) * (j - i)
                if score > bestScore:
                    secBestScore = bestScore
                    secBestPair = bestPair
                    bestScore = score
                    bestPair = (i, j)
                elif score > secBestScore:
                    secBestScore = score
                    secBestPair = (i, j)
 
        s = set((*bestPair, *secBestPair))
        if len(s) == 4:
            i, j = bestPair
            A[i], A[j] = A[j], A[i]
            i, j = secBestPair
            A[i], A[j] = A[j], A[i]
        else:
            h, k = bestPair
            A[h], A[k] = A[k], A[h]
            bS1 = -math.inf
            bP1 = (0, 0)
            for i in range(n - 1):
                for j in range(i+1, n):
                    s = (A[i] - A[j]) * (j - i)
                    if s > bS1:
                        bS1 = s
                        bP1 = (i, j)
            A[h], A[k] = A[k], A[h]
            
            h, k = secBestPair
            A[h], A[k] = A[k], A[h]
            bS2 = -math.inf
            bP2 = (0, 0)
            for i in range(n - 1):
                for j in range(i+1, n):
                    s = (A[i] - A[j]) * (j - i)
                    if s > bS2:
                        bS2 = s
                        bP2 = (i, j)
            A[h], A[k] = A[k], A[h]
 
            if bestScore + bS1 > secBestScore + bS2:
                i, j = bestPair
                A[i], A[j] = A[j], A[i]
                i, j = bP1
                A[i], A[j] = A[j], A[i]
            else:
                i, j = secBestPair
                A[i], A[j] = A[j], A[i]
                i, j = bP2
                A[i], A[j] = A[j], A[i]
 
        t = 0
        for i, x in enumerate(A):
            t += (i+1) * x
        out.append(t)
 
print("\n".join(map(str, out)))

Let the binary representation of the initial investment be $$$2^na_n + 2^{n-1}a_{n-1} + \cdots + 2^2a_2 + 2a_1 + a_0$$$. Let's see what happens when we successively floor divide by $$$2$$$:

\begin{aligned} 4 &= 2 \ &= 3 \end{aligned}

import sys, math, random
input = sys.stdin.readline
out = []
 
for _ in range(int(input())):
    n = int(input())
 
    s = "a"
    for i in range(k):
        if i % 2 == 0:
            s += "b"
        else:
            s += "a"

    out.append(s)
 
print("\n".join(out))