#define TEMPLATE_USED
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef pair<ll, ll> pl;
typedef vector<pl> vp;
const ll INF = 1001001001;
const ll LINF = 1001001001001001001;
const ll D4[] = {0, 1, 0, -1, 0};
const ll D8[] = {0, 1, 1, 0, -1, -1, 1, -1, 0};
#define _overload3(_1, _2, _3, name, ...) name
#define _rep2(i, n) for (ll i = 0; i < (n); ++i)
#define _rep3(i, a, b) for (ll i = (ll)(a); i < (ll)(b); ++i)
#define rep(...) _overload3(__VA_ARGS__, _rep3, _rep2)(__VA_ARGS__)
#define _repe2(i, n) for (ll i = 0; i <= (ll)(n); ++i)
#define _repe3(i, a, b) for (ll i = (ll)(a); i <= (ll)(b); ++i)
#define repe(...) _overload3(__VA_ARGS__, _repe3, _repe2)(__VA_ARGS__)
#define _rrep2(i, n) for (ll i = (ll)(n)-1; i >= 0; i--)
#define _rrep3(i, a, b) for (ll i = (ll)(b)-1; i >= (ll)(a); i--)
#define rrep(...) _overload3(__VA_ARGS__, _rrep3, _rrep2)(__VA_ARGS__)
#define _rrepe2(i, n) for (ll i = (ll)(n); i >= 0; i--)
#define _rrepe3(i, a, b) for (ll i = (ll)(b); i >= (ll)(a); i--)
#define rrepe(...) _overload3(__VA_ARGS__, _rrepe3, _rrepe2)(__VA_ARGS__)
#define all(x) (x).begin(), (x).end()
template <class T>
bool chmax(T &a, const T &b)
{
    if (a < b)
    {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
bool chmin(T &a, const T &b)
{
    if (b < a)
    {
        a = b;
        return 1;
    }
    return 0;
}
const string YES = "Yes";
const string NO = "No";

vl A;

void solve();

int main()
{
    cin.tie(0);
    ios::sync_with_stdio(0);
    A = vl(3);
    for (int i = 0; i < 3; ++i)
    {
        cin >> A[i];
    }
    solve();
}

// 1 <= A_i <= 100
// 入力は全て整数

// vl A
// A を並び替えて等差数列にできるなら Yes、できないなら No と出力せよ。
void solve()
{
    sort(all(A));
    cout << (A[2] - A[1] == A[1] - A[0] ? "Yes" : "No") << endl;
}

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;
typedef long long ll;
typedef vector<int> vi;

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);

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

	return 0;
}