#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
using namespace std;
using ll = long long;
const int INF = 1000000000;
const int MOD = 1000000007;
const ll llINF = 1000000000000000000;

void solve() {
  vector<int> a(3);
  rep(i, 3) cin >> a[i];
  sort(all(a));
  if (a[2] - a[1] == a[1] - a[0]) cout << "Yes" << endl;
  else cout << "No" << endl;
}

int main() {
  std::cin.tie(nullptr);
  std::ios_base::sync_with_stdio(false);
  std::cout << std::fixed << std::setprecision(15);
  solve();
  return 0;
}
#include<bits/stdc++.h>
#include<math.h>

#define    str     string
#define    sz      size()
#define    bgn      begin()
#define    ll      long long int
#define    li      long int
#define    con     continue
#define    rt      return 0
#define    fr      first
#define    sec     second
#define    pf      push_front
#define    pb      push_back
#define    vb      vct.begin()
#define    ve      vct.end()
#define    vs      vct.size()
#define    db      dq.begin()
#define    de      dq.end()
#define    ds      dq.size()
#define    ib      it.begin()
#define    ie      it.end()
#define    itf     it->first
#define    its     it->second
#define    lb      lst.begin()
#define    le      lst.end()
#define    mb      mp.begin()
#define    me      mp.end()
#define    stb     st.begin()
#define    ste     st.end()
#define    sb      s.begin()
#define    se      s.end() 
#define    NL      printf("\n")
#define   yes       printf("YES\n")
#define   no        printf("NO\n")
#define   forone    for(i=1;i<=n;i++)
#define   forzero   for(i=0;i<n;i++)
#define   sortone   sort(ara+1,ara+n+1)
#define   sortzero  sort(ara,ara+n)
#define   get(ara)  forone cin>>ara[i]
#define tc ll tc;scanf("%lld",&tc);while(tc--)

using namespace std;
int main( )
{ 
   
//tc  
{

ll i,j,k,y,n,x,m,a,b,ans=0,sum=0,cnt=0;

ll c,mx=0,mn=INT_MAX,mod=1e9+7; 

    str s,z,taj="No";
    cin>>n>>k;
    x=abs(n-k);
    if(x<=2) taj="Yes";      
    cout<<taj;
    NL;                                                                                      
 }  
         
    return 0;            
}