#include<stdio.h>
int main()
{
int i,j,n,m;
scanf("%d%d",&n,&m);
if(n<=1&&n>=-1&&m>=-1&&m<=1)
printf("yes");
else if(n<=1&&n>=-1&&m<=1&&m>=-1)
printf("yes");
else if(n>=-1&&n<=1&&m>=-1&&m<=1)
printf("yes");
else if(n>=-1&&n<=1&&m<=1&&m>=-1)
printf("yes");
else
printf("no");
return 0;
}