poj 2039 To and Fro

#include <iostream>#include <string>using namespace std;int main(){    int interval,row,i,j;    char str[210];    while(cin>>interval&&interval)    {        cin>>str;        row=strlen(str)/interval;        for(i=0;i<interval;i++) for(j=0;j<row;j++) {     if(j%2==0)         cout<<str[interval*j+i];     else          cout<<str[interval*(j+1)-1-i]; }        cout<<endl;    }    return 0;}