只有六十分...求大佬康康我

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
int main()
{
    int n,length;
    char a[51];
    cin>>n;
    cin>>a;
    length=strlen(a);
    for(int i=0;i<length;i++)
        if(a[i]+n<'z')
            printf("%c",a[i]+n);
        else
            printf("%c",a[i]+n-'z'+'a'-1);
}