#include<stdio.h>
int main(void)
{
int box[A+B+1]
int A,B,S,count;
scanf("%d",&A);
scanf("%d",&B);
scanf("%d",&S);
box[ ]=S;
count=sizeof box/sizeof(int);
if(1<=A && B<=5 && box[A+1]='-' && count==A+B+1){
printf("yes");}
else{
printf("no");}
return 0;
}