#define _CRT_SECURE_NO_WARNINGS
#include <cstdio>
#include <string>
#include <vector>
#include <algorithm>
#include <memory.h>
#include <cmath>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <ctime>
#include <iostream>
#include <functional>
#include <complex>

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<double, double> pdd;
typedef pair<pii, int> p3i;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef vector<pii> vii;
typedef vector<p3i> v3i;
typedef vector<vii> vvii;
typedef vector<p3i> vp3i;
typedef long double ld;
typedef vector<ld> vld;
typedef vector<pii> vpii;

#define pb push_back
#define mp make_pair
#define REP(i, n) for (int (i) = 0; (i) < (n); (i)++)
#define REPD(i, n) for (int (i) = (n) - 1; (i) >= 0; (i)--)
#define FOR(i, a, b) for (int (i) = (a); (i) < (b); (i)++)
#define FORD(i,a, b) for (int (i) = (a); (i) >= (b); (i)--)
#define sz(v) (int)(v).size()
#define all(v) (v).begin(), (v).end()
#define rv(v) reverse(all(v))
#define CL(v, val) memset((v), (val), sizeof((v)))
#define SORT(a) sort(all(a))
#define un(v) SORT(v), (v).resize(unique(all(v)) - (v).begin())
#define eps 1.0e-7
#define X first
#define Y second
#define bit(n) (1 << (n))
#define bit64(n) (ll(1) << (n))
#define sqr(n) ((n) * (n))
#define INF 300000005
#define MAXN 1000000

int main()
{
	int n;
	scanf("%d", &n);
	vll arr;
	REP(i, n)
	{
		ll tmp;
		scanf("%lld", &tmp);
		arr.pb(tmp);
	}
	SORT(arr);
	stack<ll> s;
	s.push(arr[0]);
	s.push(arr[1]);
	FOR(i, 2 , sz(arr))
	{
		if (sz(s) == 1)
		{
			s.push(arr[i]);
			continue;
		}
		ll tmp = s.top();
		s.pop();
		if (tmp - s.top() == arr[i] - tmp)
		{
			i--;
		}
		else
		{
			s.push(tmp);
			s.push(arr[i]);
		}
	}
	if (sz(s) == 2)
	{
		printf("YES");
	}
	else
	{
		printf("NO");
	}
	return 0;
}