#include <bits/stdc++.h>
using namespace std;
int main() {
  string d;
  char s;
  int a, b, c = 0, f = 0;
  cin >> a >> b;
  cin >> s;
  d = s;
  f = sizeof(s);
  c = 1 + a + b;
  if (d[a + 1] == '_') {
    if (f <= c) {
      if (0 < s && s < 10) {
        std::cout << "yes" << std::endl;
      } else {
        std::cout << "no" << std::endl;
      }
    } else {
      std::cout << "no" << std::endl;
    }
  } else {
    std::cout << "no" << std::endl;
  }
}
