40分蒟蒻求问

#include<iostream>
#include<cstring>
#include<string>
#include<algorithm>
#include<cstdio>
#define dd long long 
#define st string
#define bl bool
#define ch char
#define db double
using namespace std;
dd n;
st s,j;
void check(ch a,dd n)
{
    ch b='a';
    dd ans;
    ans=a-96;
    ans=ans+n;
    ans=ans%26;
    for(int i=1;i<=26;i++)
    {
        if(ans==i)
        {
            cout<<b;
            return ;
        }
        b++;
    }
}
int main()
{
    cin>>n;
    cin>>s;
    for(int i=0;i<=s.length();i++)
    {
        check(s[i],n);
    }
    return 0;
}