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#include<bits/stdc++.h>
#include <cctype>
#include <algorithm>
using namespace std;
 
int main() {
	int a,b;
  	cin >> a >> b;
  	string s;
  	cin >> s;
  	string _s = s.substr(0,a)+s.substr(a+1,b);
  	if(s[a]=='-') {
      	if(std::all_of(_s.cbegin(), _s.cend(), isdigit)) {
        	cout << "yes" << endl;
          	return 0;
        }
    }
  	cout << "no" << endl;
  	return 0;
}