#include <bits/stdc++.h>
#include <algorithm>
using namespace std;

int main() {
    int a, b, c;
    cin >> a >> b >> c;

    if (a > b) {
        swap(a, b);
    }
    if (b > c) {
        swap(b, c);
    }
    if (a > b) {
        swap(a, b);
    }

    if (c - b == b - a) {
        cout << "Yes" << endl;
    } else {
        cout << "No" << endl;
    }
}

#include <bits/stdc++.h>
using namespace std;
#define ll long long int
#define deb(x) cout << #x << " " << x << endl;
#define mod 1000000007
#define fast std::ios::sync_with_stdio(false), cin.tie(NULL), cout.tie(NULL);
#define endl "\n"

const ll INF = 1e18;
const ll NEGINF = -1 * INF;

/*NOTES: Take care of ll vs int
         Never use an iterator after erasing it
*/

void solve()
{
    vector<int> 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" << endl;
    }
    else
    {
        cout << "No" << endl;
    }
}

int main()
{
    fast;
#ifndef ONLINE_JUDGE
    freopen("/home/kalit/Desktop/Data Structures-Algo-Competitive/src/codeforces/input.txt", "r", stdin);
    freopen("/home/kalit/Desktop/Data Structures-Algo-Competitive/src/codeforces/output.txt", "w", stdout);
#endif
    int T = 1;
    while (T--)
    {
        solve();
    }
    //cout<< "Done in " << clock() / CLOCKS_PER_SEC <<"sec"<< endl;
    return 0;
}