#include<bits/stdc++.h>
typedef long long ll, LL;
using namespace std;
#define pb push_back

void solve() {
	int n;
	cin >> n;
	int s[n];
	for(int i = 0; i < n; i++) {
		scanf("%1d", &s[i]);
	}
	if(n==2&&s[0]!=s[1]) cout << "YES" << endl;
	else cout << "NO" << endl;
}

int main() {
//	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	
	int t = 1;
//	cin >> t;
    while(t--) {
    	solve();
	}
	
	return 0;
}