#include <bits/stdc++.h>
using namespace std;
int main() {
  int A, B, count = 0;
  char S[10];
  scanf("%d%d", &A, &B);
  for (int i = 0; i <= A + B + 1; i++) {
    scanf("%c", &S[i]);
    if (i == A + 1) {
      if (S[i] != '_') {
        count = 1;
      }
    } else {
      if (S[i] == '_') {
        count = 1;
      }
    }
  }
  if (count == 0) {
    printf("Yes");
  } else {
    printf("No");
  }
  return 0;
}
