#include <bits/stdc++.h>
#define LL long long

using namespace std;

int a1, a2, a3;

int main() {
  cin.tie(0), cout.tie(0);
  ios::sync_with_stdio(false);
  cin >> a1 >> a2 >> a3;
  cout << (a1 - a2 == a2 - a3 || a1 - a3 == a3 - a2 || a2 - a1 == a1 - a3 || a2 - a3 == a3 - a1 || a3 - a1 == a1 - a2 || a3 - a2 == a2 - a1 ? "Yes" : "No") << endl;
  return 0;
}

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define SZ(x) ((int)(x).size())
#define FOR(var, begin, end) for (int var = (begin); var <= (end); var++)
#define RFOR(var, begin, end) for (int var = (begin); var >= (end); var--)
#define REP(var, length) FOR(var, 0, length - 1)
#define RREP(var, length) RFOR(var, length - 1, 0)
#define EACH(value, var) for (auto value : var)
#define SORT(var) sort(var.begin(), var.end())
#define REVERSE(var) reverse(var.begin(), var.end())
#define RSORT(var) SORT(var); REVERSE(var)
#define OPTIMIZE_STDIO ios::sync_with_stdio(false); cin.tie(0); cout.precision(10); cout << fixed
#define endl '\n'

const int INF = 1e9;
const int MOD = 1e9 + 7;
const ll LINF = 1e18;

void solve(istream& cin, ostream& cout) {
  vector<int> a(3);
  REP(i, 3) cin >> a[i];
  SORT(a);
  if (a[2] - a[1] == a[1] - a[0]) cout << "Yes" << endl;
  else
    cout << "No" << endl;
}

#ifndef TEST
int main() {
  OPTIMIZE_STDIO;
  solve(cin, cout);
  return 0;
}
#endif
