#include <bits/stdc++.h>
using namespace std;
int main() {
  int A, B;
  string s;
  cin >> A >> B >> s;
  sort((s).begin(), (s).end());
  if (s[0] == '-' && s[1] >= '0' && s[A + B] <= '9') {
    cout << "Yes\n";
  } else
    cout << "No\n";
  return 0;
}
