#include <bits/stdc++.h>
using namespace std;
typedef unsigned long long ull;
typedef long long ll;
typedef string str;
const ll mod = 1e9 + 7;
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    ll n, p;
    str s;
    char k;
    cin >> n >> s >> p >> k;
    s[p-1] = k;
    cout << s;
    return 0;
}