To and Fro

400. To and Fro Problem code: TOANDFRO

 #include<iostream>
 using namespace std;
 int main()
 {
     int columns,n,m;
     while (1)
     {
            cin>>columns;
            if (columns==0)
                break;
         string s;
         cin >> s;
         string r(s);

         int rows = s.size() / columns;
         for (int i=0; i<s.size(); i++)
         {
            m = i/columns;
            m%2==0?n=i%columns:n = columns-1-i%columns;   
            r[n*rows+m] = s[i];
         }
         cout << r << endl;
     }
     return 0;
 }