一本通1056

//qf
#include <bits/stdc++.h>
#define f(i,j,n) for(register int i=j;i<=n;i++)
using namespace std;
typedef long long ll;
inline ll read(){
	ll x=0;
	int f=1;
	char ch=getchar();
	while(!isdigit(ch)) {
		if(ch=='-') f=-1;
		ch=getchar();
	}
	while(isdigit(ch)) x=(x<<1)+(x<<3)+ch-48,ch=getchar();
	return x*f;
}
int x=read(),y=read();
inline bool check(){
	if(x<-1 or x>1) return false;
	if(y<-1 or y>1) return false;
	return true;
}
signed main(){
	puts(check()?"yes":"no");
	return 0;
}