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

template<typename T>
ostream& operator<<(ostream &os, vector<T> &v){
    string sep = " ";
    if(v.size()) os << v[0];
    for(int i=1; i<v.size(); i++) os << sep << v[i];
    return os;
}

template<typename T>
istream& operator>>(istream &is, vector<T> &v){
    for(int i=0; i<v.size(); i++) is >> v[i];
    return is;
}

#ifdef DBG
void debug_(){ cout << endl; }
template<typename T, typename... Args>
void debug_(T&& x, Args&&... xs){
    cout << x << " "; debug_(forward<Args>(xs)...);
}
#define dbg(...) debug_(__VA_ARGS__)
#else
#define dbg(...)
#endif

int main() {
    ios_base::sync_with_stdio(false);
    cout << setprecision(20) << fixed;
    vector<int> a(3);
    cin >> a;
    sort(a.begin(), a.end());

    cout << (a[2]-a[1]==a[1]-a[0]?"Yes":"No") << endl;

    return 0;
}
#include<iostream>
#include<bits/stdc++.h>
#define mod 1000000007
#define int long long
#define pii pair<int,int>
#define pb(x) push_back(x)
#define lbound lower_bound
#define ubound upper_bound
#define gcd(a,b) __gcd(a,b)
#define all(v) v.begin(),v.end()
#define bits(x) __builtin_popcountll(x)
#define heap_min priority_queue<int,vector<int>,greater<int>>
#define heap_max priority_queue<int>
#define precision(x) cout << setprecision(x) << fixed;
#define printv(v) for(auto p : v) cout << p << " ";
#define printa(a,n) for(int i = 1 ; i <= n ; i++) cout << a[i] << " ";
#define fast ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);

using namespace std;



void solve()
{
  int n;
  map<string,int>mp;
  string s;
  set<string>ss;
  cin >> n;
  for(int i = 0 ; i  < n ; i++){
    cin >> s;
    if(s[0]=='!'){
      mp[s] = 1;
    }
    else{
      ss.insert(s);
    }
  }

  string ans = "*";
  for(auto p : ss){
    if(mp["!"+p] == 1){
      ans = p;
      break;
    }
  }

  if(ans == "*"){
    cout << "satisfiable";
    return;
  }

  cout << ans;

}


int32_t main()
{
   fast;
   #ifndef ONLINE_JUDGE
   freopen("goodluckin.txt","r",stdin);
   freopen("goodluckout.txt","w",stdout);
   #endif
   clock_t beg = clock();
   solve();
   clock_t end = clock();
   fprintf(stderr, "Time taken : %.3f sec\n", double(end - beg) / CLOCKS_PER_SEC , 184);
   return 0;

}


