#include<bits/stdc++.h>
using namespace std;

int main(){
	int a,b;
  	string s;
    
  	cin >> a >> b >> s;
  	for(int i = 0; i < a; i++){
      if(s[i] == "-"}{
		cout << "No" << endl;
        return 0;
      }
    }
   if(s[a] != "-"){
   cout << "No" << endl;
   return 0;
   }
  for(int i = a + 1; i < a + 1 + b; i++){
    if(s[i] == "-"){
    	cout << "No" << endl;
    	return 0;
    }
  }
 cout << "Ok" << endl;
         return 0;
         }