Source Code

Problem: 2039  User: O_Q 
Memory: 84K  Time: 0MS 
Language: C  Result: Accepted 

Source Code 
#include<stdio.h>
#include<string.h>

int main()
{
	char s[201];
	int n,m,i,j,k,t;
	while(scanf("%d",&n),n)
	{
		scanf("%s",s);
		m=strlen(s);
		for(i=k=1;i<=n;i++,k+=2)
			for(j=i,t=k;j<=m;j+=2*n-t,t=2*n-t)
				putchar(s[j-1]);
		printf("\n");
	}
	return 0;
}