#include <bits/stdc++.h>   using namespace std;   int N, i, j;   string S, R;   int main() {     ios_base::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     cin >> N >> S;     for (i = N - 2; i >= 0; i -= 2) {       R = R + S[i];     }     if (N % 2 == 0)       i = 1;     else       i = 0;     for (i = i; i < N; i += 2) {       R = R + S[i];     }     cout << R << endl;   }   