#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int main()
{
	ios_base::sync_with_stdio(false); cin.tie(NULL);

	int A[3];
	for (int i = 0; i < 3; ++i)
		cin >> A[i];
	sort(A, A + 3);
	if (A[0] + A[2] - 2 * A[1] == 0)
		cout << "Yes\n";
	else
		cout << "No\n";
}

#include <iostream>
#include <string>
#include <math.h>
#include <vector>
#include <algorithm>
#include <iomanip>
#include <set>
#include <queue>
#include <deque>
#include <map>
#include <stack>
#include <cmath>
#include <stdio.h>
using namespace std;

#define mod 1000000007
#define mod2 998244353
#define ten5 100005
#define ten52 200005
#define ten53 300005
#define ten6 1000005
#define PI 3.1415926
#define pb(x) push_back(x)
#define all(x) x.begin(),x.end()
#define mkpr(x1,x2) make_pair(x1,x2)

#define _debug 1
#if _debug
#endif // _debug

typedef long long int ll;
typedef unsigned long long int ull;

ll num[100];

void solve()
{
    for(int i=0;i<3;i++)
    {
        for(int j=i+1;j<3;j++)
        {
            if(num[i] > num[j])
                swap(num[i],num[j]);
        }
    }
}

int main(void)
{
    ll m,n,i=0,j=0,k=1;
    while(i<3)
    {
        cin>>num[i++];
    }

    solve();
    if(num[2] - num[1] == num[1] - num[0]) cout<<"Yes";
    else cout<<"No";
    return 0;
}
