#include <bits/stdc++.h>
#include <vector>
#include <locale>
#include <string>
#include <stdio.h>
#include <math.h>
using namespace std;


int main() {
  int a1, a2, a3;
  cin >> a1 >> a2 >> a3;
  if(a3-a2 == a2-a1) cout << "Yes" << endl;
  else if(a2-a3 == a3-a1) cout << "Yes" << endl;
  else if(a3-a1 == a1-a2) cout << "Yes" << endl;
  else if(a1-a3 == a3-a2) cout << "Yes" << endl;
  else if(a2-a1 == a1-a3) cout << "Yes" << endl;
  else if(a1-a2 == a2-a3) cout << "Yes" << endl;
  else cout << "No" << endl;
  
}
#include <bits/stdc++.h>
using namespace std;
#define __hh__ ios_base::sync_with_stdio(false); cin.tie(0);
#define ll long long
#define all(x) (x).begin(),(x).end()
#define vi vector<int>
#define vl vector<long long>
#define vs vector<string>
#define vd vector<double>
#define vvi vector<vector<int>>
#define vvl vector<vector<long long>>
#define vvs vector<vector<string>>
#define mii map<int,int>
#define msi map<string,int>
#define rep(i,n) for(int i=0; i<n; i++)
#define repr(i,s,n) for(int i=s; i<n ;i++)
#define repl(i,n) for(ll i=0; i<n; i++)
#define reprl(i,s,n) for(ll i=s; i<n ;i++)
const double PI=3.14159265358979323846;
const int INF=20e8;
const ll INFL=92e12;



int main() {
  __hh__

  vi v(3);
  rep (i, 3) cin >> v[i];
  sort(all(v));
  bool ans = false;
  if (v[1]-v[0]==v[2]-v[1]) ans = true;
  cout << (ans ? "Yes" : "No") << "\n";

}
