import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int a = sc.nextInt();
		int b = sc.nextInt();
		String s = sc.next();
               boolean flg = true;
		for(int i = 0; i < a; i++){
                     if( "-".equals(s[i] )) flg == false;
               }
               if ( !("-".equals(s[i] ))) flg == false;
		for(int i = a+1; i < b; i++){
                     if( "-".equals(s[i] )) flg == false;
               }
              if (flg)                System.out.print("yes");
             else  System.out.print("no");
	}
}