#include<bits/stdc++.h>
using namespace std;
using ll=long long;

#include<atcoder/modint>
using namespace atcoder;
using mint=modint1000000007;

void solve(){
    int N,X;
    string S;
    char C;
    cin>>N>>S>>X>>C;
    S[X-1]=C;
    cout<<S<<"\n";
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    int T=1;
    // cin>>T;
    while(T--)solve();
}