#include <bits/stdc++.h>

using namespace std;

#define fst(t) std::get<0>(t)
#define snd(t) std::get<1>(t)
#define thd(t) std::get<2>(t)

using ll = long long;
using P = std::tuple<int,int>;

const int dx[8] = {-1, 1, 0, 0, -1, -1, 1, 1}, dy[8] = {0, 0, -1, 1, -1, 1, -1, 1};

int kamo[100000], diffs[100000];
set<int> s;

int main(){
    //*
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);
    /*/
      /*/

    int N;
    std::cin >> N;

    for(int i=0;i<N;++i){
        std::cin >> kamo[i];

        s.insert(kamo[i]);
    }
    
    if(s.size() != N){
        puts("NO");
        return 0;
    }
    
    sort(kamo, kamo+N);
    adjacent_difference(kamo, kamo+N, diffs);
    
    for(int i=1;i<N;++i){
        if(diffs[i] != diffs[1]){
            puts("NO");
            return 0;
        }
    }

    puts("YES");
}