#include<stdio.h>
#include<string.h>
int main(){
    int len,i,j,k;
	char s[220];
	while(scanf("%d%*c",&len)!=EOF){
		if(len==0) break;
		gets(s);
		for(i=1;i<=len;i++){
			for(j=i-1,k=1;j<strlen(s);k++,j+=k%2?2*i-1:(2*len-2*i+1)){
                		printf("%c",s[j]);
			}
		}
    printf("\n");
	}
return 0;
}