#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, c;
  cin >> a >> b >> c;
  if (b > a) {
    if (b - a == c) cout << "Yes" << endl;
  }
  if (a > b) {
    if (a - b == c) cout << "Yes" << endl;
  } else
    cout << "No";
  return 0;
}
