WA了，代码如下

#include<bits/stdc++.h>
using namespace std;
int n;
char s[100];
int main()
{
	scanf ("%d",&n);
	scanf ("%s",&s);
	if (n == 26) 
	{
		printf ("%s",s);
		return 0;
	}
	for (int i = 0;s[i] != '\0';i++)
	{
		s[i] = s[i] + n;
		if (s[i] > 'z')
		{
			s[i] = s[i] - 26;
		}
	}
	printf ("%s",s);
	return 0;
}