#include<iostream>
using namespace std;
int main(){
    int a,b, thief[10000],i=0;
    cin>>a;
    cin>>b;
    int count = 0;
    for (int i = 0;i<10000;i++){
        thief[i] = i;
    //    cout<<thief[i]<<" ";

    }
    for(i=0;i<10000;i++){
        //cout<<"first"<<i<<endl;
        if(a==thief[i]||b==thief[i+1]){
            count++;

        }
    //    cout<<"thief["<<i<<"]"<<thief[i]<<"\t"<<"thief["<<i+1<<"]"<<thief[i+1]<<endl;
        i=i+1;
        //cout<<"thief"<<i<<endl;


    }
    if(count>0)
    cout<<"yes";
    else
    cout<<"no";
}