#include <cassert>
#include <bits/stdc++.h>
using namespace std;

#define rep(i,n) for(int i = 0; i < (int)(n); i++)
constexpr int inf = 2e9;
#include <atcoder/all>
using namespace atcoder;

#include <boost/multiprecision/cpp_int.hpp>
#include <boost/math/common_factor_rt.hpp>
namespace mp = boost::multiprecision;
using ll = long long;
int main()
{
    int N;
    string S;
    cin >> N >> S;
    int X;
    cin >> X;
    X--;
    char c;
    cin >> c;
    S[X] = c;
    cout << S << "\n";
}