#include <bits/stdc++.h>
using namespace std;
using s64 = signed long long;
using u64 = unsigned long long;
using f128 = long double;
#define LOGVAR(var) cout << #var << ": " <<  var << endl

int main()
{
    vector<s64> a(3);
    cin >> a[0] >> a[1] >> a[2];

    sort(a.begin(), a.end());

    if(a[2] - a[1] == a[1] - a[0])
    {
        cout << "Yes" << endl;
    }
    else
    {
        cout << "No" << endl;
    }

    return 0;
}

#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace __gnu_pbds;
using namespace std;

#define ff                  first
#define ss                  second
#define pb                  push_back
#define eb                  emplace_back
#define mp                  make_pair
#define lb                  lower_bound
#define ub                  upper_bound
#define setbits(x)          __builtin_popcountll(x)
#define zrobits(x)          __builtin_ctzll(x)
#define sz(v)               (int)v.size()
#define ps(y)               cout << fixed << setprecision(y)
#define ms(arr, v)          memset(arr, v, sizeof(arr))
#define all(v)              v.begin(), v.end()
#define rall(v)             v.rbegin(), v.rend()
#define trav(x, v)          for(auto &x: v)
#define w(t)                int t; cin >> t; while(t--)
#define rep0(i, n)          for(int i = 0; i < n; i++)
#define rrep0(i, n)         for(int i = n - 1; i >= 0; i--)
#define rep1(i, n)          for(int i = 1; i <= n; i++)
#define rrep1(i, n)         for(int i = n; i > 0; i--)
#define inp(arr, n)         rep0(i, n) cin >> arr[i];
#define rep(i, a, b)        for(int i = a; i <= b; i++)
#define rrep(i, a, b)       for(int i = a; i >= b; i--)

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<ll, ll> pii;
typedef vector<ll> vi;
typedef vector<vi> vvi;
typedef vector<pii> vp;
typedef vector<bool> vb;
typedef vector<string> vs;
typedef map<ll, ll> mii;
typedef map<char, ll> mci;
typedef priority_queue<ll> pq_mx;
typedef priority_queue<ll, vi, greater<>> pq_mn;
typedef tree<ll, null_type, less<>, rb_tree_tag, tree_order_statistics_node_update> pbds;
/*
 * find_by_order(i) -> returns an iterator to the element at ith position (0 based)
 * order_of_key(i)  -> returns the position of element i (0 based)
 */

const int N = 2e5 + 5;
const int mod = 1e9 + 7;
//const int mod = 998244353;
const ll inf = 1e18;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

void fio() {
    ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
}

int main() {
    fio();

    vi a(3);
    inp(a, 3)
    sort(all(a));
    if(a[1] - a[0] == a[2] - a[1]) cout<<"Yes";
    else cout<<"No";
    
    return 0;
}