#include<bits/stdc++.h>
using namespace std;
int main()
{
	int x,y,a[3]={-1,-1,-1};
	cin>>x>>y;
	a[x]++;
	a[y]++;
	if(x==y)
	{
		cout<<x;
		return 0;
	}
	for(int i=0;i<3;i++)
	{
		if(a[i]==-1) cout<<i;
	}
	return 0;
}
#include <bits/stdc++.h>
using namespace std;
#define ll long long
template <class T = ll> using P = pair<T,T>;
template <class T = ll> using V = vector<T>;
template <class T = ll> using VV = V<V<T>>;
#define rep(i,n) for(int i=0; i<(n);++i)
#define repp(i, l, r) for(int i = (l); i < (r); ++i)
#define pb push_back
#define all(v) (v).begin(), (v).end()

int main()
{
    V<int> a(3);
    rep(i,3) cin >> a[i];
    sort(a.begin(), a.end());
    if(a[1] - a[0] == a[2] - a[1]){
        cout << "Yes" << endl;
    }else{
        cout << "No" << endl;
    }
    
    return 0;
}