#include <bits/stdc++.h>
using namespace std;
#define vi vector<int>
#define fo(a,b,c) for(int a=b;a<c;a++)
#define int long long int
#define ff first
#define ss second
#define pb push_back
#define fastio ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
const int mod = 1e9 + 7;
const int cmod = 998244353;
const int N = 3e5 + 5;
const int inf = 1e18 + 2;
int power(int a,int b)
{
    if(b==0)
    return 1;
    else if(b%2==0)
    {
    int c=power(a,b/2);
    return (c*c)%mod;
    }
    else
    return ((a%mod)*(power(a,b-1)%mod))%mod;
}
void solve(int Case)
{
    vi v(3);
    fo(i,0,3)
    cin>>v[i];
    sort(v.begin(),v.end());
    if(v[1]-v[0]==v[2]-v[1])
    {
        cout<<"Yes";
        goto a;
    }
    sort(v.begin(),v.end(),greater<int>());
    if(v[1]-v[0]==v[2]-v[1])
    {
        cout<<"Yes";
        goto a;
    }
    cout<<"No";
    a:;
}
int32_t main()
{
    fastio
    int testcase = 1;
    //cin >> testcase;
    int Case = 1;
    while(testcase --)
    {
        solve(Case);
    }
    return 0;
}
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int main(){

    int a, b, c;
    cin >> a >> b >> c;
    if(a > b) swap(a, b);
    if(a > c) swap(a, c);
    if(b > c) swap(b, c);
    if(b - a == c - b) cout << "Yes" << endl;
    else cout << "No" << endl;
    return 0;
}