#include<bits/stdc++.h>
using namespace std;
int main()
{
	int x,y,v;
	cin>>x>>y;
	if(x<=1&&x>=0)	v++;
	if(x>=-1&&x<=0)	v++;
	if(y<=1&&y>=0)	v++;
	if(y>=-1&&y<=0)	v++;
	if(v==2)
		cout<<"yes"<<endl;
	else
		cout<<"no"<<endl;
	
	
}