#include <bits/stdc++.h>
using namespace std;
int main() {
  int A, B;
  cin >> A >> B;
  string S;
  cin >> S;
  string s1 = S.substr(0, A);
  string s2 = S.substr(A + 1, B);
  for (int i = 0; i < A; ++i) {
    if (s1[i] >= '0' && s1[i] <= '9') {
    } else {
      cout << "No" << endl;
      exit(0);
    }
  }
  for (int i = 0; i < B; ++i) {
    if (s2[i] >= '0' && s2[i] <= '9') {
    } else {
      cout << "No" << endl;
      exit(0);
    }
  }
  cout << "Yes" << endl;
}
