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

# define endl "\n"
# define io_boost std::ios_base::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);
typedef unsigned long long int ulli;
typedef long long int lli;
typedef unsigned int ui;

int a[3];

int main(){
    cin >> a[0] >> a[1] >> a[2];
    if(2 * a[1] == a[2] + a[0]) cout << "Yes" << endl;
    else if(2 * a[0] == a[2] + a[1]) cout << "Yes" << endl;
        else if(2 * a[2] == a[0] + a[1]) cout << "Yes" << endl;
        else cout << "No" << endl;
    return 0;
}
#include<bits/stdc++.h>
#define endl '\n'
#define ri register
#define QAQ(m, n) for(ri ll i = m;i <= n;i++)
#define QWQ(m, n) for(ri ll j = m;j <= n;j++)
#define uQAQ(n, m) for(ri ll i = n;i >= m;--i)
#define uQWQ(n, m) for(ri ll j = n;j >= m;--j)
#define ALL(a) a.begin(), a.end()
#define all(a, n) a + 1, a + n + 1
#define fin(a) freopen(a, "r", "stdin")
#define fout(a) freopen(a, "w", "stdout")
#define pb push_back
#define mkp make_pair
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
ll a[4];
int main ()
{
	std::cin.tie (0);
	std::ios::sync_with_stdio (false);
	cin >> a[1] >> a[2] >> a[3];
	sort(all(a,3));
  	cout << ((a[3]-a[2]==a[2]-a[1])?("Yes"):("No"));
	return 0;
}