#include <bits/stdc++.h>
using namespace std;
#define int long long
#define rep(i,j)  for(int i=0; i<j; i++)
#define vi vector<int>
#define vvi vector<vector<int>>
#define sr(a) sort(a.begin(),a.end())

signed main(){
  int n; cin>>n;
  string s; cin>>s;
  int x; cin>>x;
  char c; cin>>c;
  s[x-1]=c;
  cout<<s<<endl;
}