#include <iostream>
#include <vector>
using namespace std;

int eat_subtree( const vector<int>& v, int sum, int i ) {
	if( sum == 0 )           return i;
	if( i<0 || i==v.size() ) return -1;
	return eat_subtree( v, sum-v[i], eat_subtree(v,sum-v[i],i+1) );
}

bool solve( const vector<int>& v ) {
	for(int a=v[0],i=1; i!=v.size(); a+=v[i++])
		if( eat_subtree(v,a,0) == v.size() )
			return true;
	return false;
}

int main() {
	for(int N; cin>>N,N;) {
		vector<int> v(N);
		for(int i=0; i!=N; ++i)
			cin >> v[i];
		cout << (solve(v)?"yes":"no") << endl;
	}
}