#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b;
  string s;
  cin >> a >> b >> s;
  string ans = "Yes";
  for (int i = 0; i < a; i++) {
    if (!(s[i] >= '0' && s[i] <= '9')) ans = "No";
  }
  for (int i = a + 1; i < a + b + 1; i++) {
    if (!(s[i] >= '0' && s[i] <= '9')) ans = "No";
  }
  cout << ans << endl;
}
