#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b;
  int i;
  string s, s1, s2;
  cin >> a >> b;
  cin >> s;
  if (strncmp("-", &s[a], 1) == 0) {
    s1 = s.substr(0, a);
    s2 = s.substr(a + 1, b);
    if (s1.size() == a && s2.size() == b) {
      cout << "yes" << endl;
    } else {
      cout << "no" << endl;
    }
  } else {
    cout << "no" << endl;
  }
  return 0;
}
