#include <bits/stdc++.h>
using namespace std;
int main()
{
    int a[3];
    cin >> a[0] >> a[1] >> a[2];
    sort(a,a+3);
    if((a[2] - a[1]) == (a[1] - a[0]) ){
        cout << "Yes" << endl;
    }
    else cout << "No" << endl;
    return 0;
}
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
int main() {
    set<ll>s;
    map<ll, ll>mp;
    ll d = 0;
    for(ll i = 0; i < 3; i++) {
        ll x; cin >> x;
        s.insert(x);
        mp[x]++;
        d = x;
    }
    if(s.size() == 3) {
        cout << 0 << '\n';
        return 0;
    }

    ll ans = 0;
    if(s.size() == 1) {
       cout << d << '\n';
       return 0;
    }

    for(auto i : mp) {
        if(i.second != 2) d = i.first;
    }

    cout << d << '\n';


}
