//
// Created by Ki Ageng Satria Pamungkas on 5/27/17.
//
#include <iostream>
#include <string>
using namespace std;
int main(){
int n, dmy, x;
string s;
bool sia;
cin >> n;
while( n != 0){
cin >> s;
x = 1;
for (int i = 0; i <n ; ++i) {
dmy = i;
sia = true;
while(dmy <=s.length()){
cout << s[dmy];
if(sia){
dmy += 2 * n - x;
sia = false;
}else{
dmy += x;
sia = true;
}
}
x += 2;
}
cout << endl;
cin >> n;
}
}
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