#include<bits/stdc++.h>
using namespace std;
int main(){
  vector<int>data(3);
  for(int i=0;i<3;i++){
    cin>>data[i];
  }
  sort(data.begin(),data.end());
  if(data[0]-data[1]==data[1]-data[2]){
    cout<<"Yes"<<endl;
  }
  else{
    cout<<"No"<<endl;
  }
}
#include<stdio.h>
#define Swap(a,b) do{typeof(a) T=(a);a=b;b=T;}while(0)
static inline int Min(int a,int b){return a<b?a:b;}
static inline int IN(void)
{
  int x=0,f=1,c=getchar();while(c<48||c>57){if(c==45){f=-f;}c=getchar();}
  while(c>47&&c<58){x=x*10+c-48,c=getchar();}return f*x;
}
int main(void)
{
  int A=IN(),B=IN(),C=IN(),x=A+B+C;if(x!=x/3*3){return !puts("No");}
  if(A>B){Swap(A,B);}if(B>C){Swap(B,C);}if(A>B){Swap(A,B);}
  return !puts(C+A==2*B?"Yes":"No");
}