#include <bits/stdc++.h>
using namespace std;
void submain(int a, int q, string S) {
	while (q--) {
		int n;
		cin >> n;
		if (n==1) {
			int x;
			char y;
			cin >> x >> y;
			S[x] = y;
		}
		else {
			char y;
			cin >> y;
			if (S[0] == y) cout << "Yes" << endl;
			else cout << "No" << endl;
		}
	}
	return;
}
int main() {
  int a, q;
  cin >> a >> q;
  string S;
  cin >> S;
  if (a == 1) {
  	submain(a, q, S);
  	return 0;
  }
  set<string> s;
  for (int i = 1; i <= min(a, 1000); 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;
  		}
  	}
  }
}