The title says it's for beginners, but the blog post says it is only for high level understanding.

I was looking through your solution http://codeforces.me/contest/585/submission/17410169 and having some problems in understanding some parts , i am writing what i understood could you reply whether i am correct or not ?

temp1 = (ModPow(2, n, MOD) — 1 + MOD) % MOD; // all the subsets excluding the empty one are taken

for (i = 1; i <= N; i++) {
    g[i] = h[i] = 0;
    if (u[i] == 0)
      continue;
    for (j = i; j <= N; j += i)
      g[i] += c[j];
    temp2 = u[i] * (ModPow(2, g[i], MOD) - 1);
    h[i] = (temp2 + MOD) % MOD;
    temp1 = (temp1 - temp2 + MOD) % MOD;
  }

// then we are iterating over all possible numbers allowed and for those numbers containing no square factors as calculated by the mobius function, for a particular value we are taking all subsets having multiples as this number and subtracting the subsets possible excluding the empty one from the temp1 .So after loop in temp1 we are having count of subsets having gcd as 1.

answer = n * temp1; // the man is coming in n instances so we are first assuming that for whatever number he chooses we will always give the complete set that is all those subsets having gcd equal to one so that since the gcd is initially one any number he chooses , the combined gcd would be one.

for (j = 2; j <= N; j++) {
    answer = (answer + (g[j] * h[j]) % MOD + MOD) % MOD;
  }

// this loop is troubling me assuming he takes number j why are we adding this thing the h[j] is the number of subsets having gcd j so we are violating the condition . Can you please explain me?

Thank You for the tutorials

I've seen this blog to come up in recent actions a lot of time. Whenever I open it, there is no new comment that I can see. Also the blog text has just 1 edit. Why does this happen?