#include <bits/stdc++.h>
using namespace std;
char n;
int a, b;
int main() {
  cin >> a >> b;
  for (int s = 0; s < a; s++) cin >> n;
  if (n < '0' || n > '9') cout << "No" << endl;
  return 0;
  cin >> n;
  if (n != '-') cout << "No" << endl;
  return 0;
  for (int s = 0; s < b; s++) cin >> n;
  if (n < '0' || n > '9') cout << "No" << endl;
  return 0;
  cout << "Yes" << endl;
  return 0;
}
