#include <bits/stdc++.h>
bool check_int(std::string str) {
  if (std::all_of(str.cbegin(), str.cend(), isdigit)) {
    return true;
  }
  return false;
}
int main() {
  int A, B;
  std::string S, S_a, S_b, S_c;
  int J;
  std::cin >> A >> B;
  std::cin >> S;
  S_a = S.substr(0, A - 1);
  S_b = S.substr(A + 1, B - 1);
  S_c = S.substr(A, A);
  if (check_int(S_a) && check_int(S_b) && !check_int(S_c))
    std::cout << "Yes" << std::endl;
  else
    std::cout << "No" << std::endl;
  return 0;
}
