My solution of code forces round div 3 for C (train queries) was hacked and I didn't the case where I would fail.Help me find that case . Thanks in advance

Here is my code ```def solve(): d = defaultdict(list)

# n = int(input())
# s=input()
e=input()
n,m=list(map(int,input().split()))
#
lis = list(map(int, input().split()))
# lis1=input().split()
# lis2 = list(map(int, input().split()))
# lis3 = list(map(int, input().split()))
# n,r,b=list(map(int,input().split()))
# order=list(map(int,input().split()))
# r2,c2=list(map(int,input().split()))
# ans=[[-1 for _ in range(m)] for _ in rnage(n)]
for i,ele in enumerate(lis):
    d[ele].append(i)
for _ in range(m):
    u,v=list(map(int,input().split()))
    if(u not in d or v not in d):
        print("NO")
        continue
    if(d[u][0]<d[v][-1]):
        print("YES")
    else:
        print("NO")

```