#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, flag = 0;
  string s;
  cin >> a >> b >> s;
  for (int i = 0; i < a + b + 1; i++) {
    if (s[i] == '-')
      continue;
    else
      flag++;
  }
  if (flag == a + b)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
  return 0;
}
