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

using ll = int64_t;
using ul = uint64_t;
using ld = long double;
using vi = vector<int>;
using vd = vector<double>;
using vc = vector<char>;
using vs = vector<string>;
using vb = vector<bool>;
using vl = vector<ll>;
using vvi = vector<vi>;
using vvd = vector<vd>;
using vvc = vector<vc>;
using vvb = vector<vb>;
using vvl = vector<vl>;
using mint = modint998244353;
using vm = vector<mint>;

int main() {
  int N,X;
  string S;
  char C;
  cin >> N >> S >> X >> C;
  S[X - 1] = C;
  cout << S << endl;
  return 0;
}