#include <bits/stdc++.h>
using namespace std;
//60取れたら本望
int main() {
  int a, q;
  cin >> a >> q;
  string S;
  cin >> S;
  set<string> s;
  for (int i = 1; i <= a; i++) {
  	//i文字のものをセットに追加
  	for (int k = 0; k <= a-i; k++) {
  		string x;
  		for (int m = k; m < k+i; m++) {
  			x += S[m];
  		}
  		s.insert(x);
  	}
  }
  while (q--) {
  	int x;
  	cin >> x;
  	if (x==1) {
  		int z;
  		cin >> z;
  		char y;
  		cin >> y;
  		S[z] = y;
  	}
  	else {
  		string a;
  		cin >> a;
  		if (s.count(a)) {
  			cout << "Yes" << endl;
  		}
  		else {
  			cout << "No" << endl;
  		}
  	}
  }
}