> #include <iostream>
> #include <cstring>
> using namespace std;
> int main()
> {
> 	int n,i,j;
> 	char message[201],ch;
> 	while(cin >> n && n != 0){
> 		cin >> message;
> 		int length = strlen(message);
> 		for(i = n;i < length;i += n * 2)
> 			for(j = i;j < (n * 1.0 / 2 + i);j++){
> 				ch = message[j];
> 				message[j] = message[2 * i - 1 + n - j];
> 				message[2 * i - 1 + n - j] = ch;
> 			}
> 		j= 1;
> 		for(i = 0;i <= 201;i += n){
> 			if(i >= length)
> 				i = j++;
> 			cout << message[i];
> 			if(i == length - 1)
> 				break;
> 		}
> 		cout << endl;
> 	}
> 	return 0;
> }

数组开大点看看，我就是开小了