#include <bits/stdc++.h> #define rep(i,n) for(int i=0;i<n;i++) #define REP(i,a,b) for(int i=a;i<b;i++) using ll = long long; using ull = unsigned long long; using namespace std; int N; int x[1000000]; void solve() { cin >> N; rep(i,N) cin >> x[i]; sort(x, x+N); reverse(x, x+N); int sub = x[0] - x[1]; bool f = true; REP(i,2,N) { if(x[i-1] - x[i] != sub || x[i-1] - x[i] == 0) { f = false; break; } } cout << (f == true ? "YES" : "NO") << endl; } int main(){cin.tie(0);ios_base::sync_with_stdio(false);solve();return 0;}