#50365: c++解
momo19990825@gmail.com
(戴千鈞)
#include<bits/stdc++.h>
using namespace std;
int main(){
int n;
while(cin>>n){
int sum =0, score;
for (int i = 0;i<n;++i){
cin>>score;
sum += score;}
double avg = sum*1.0/n;
if (avg > 59){
cout << "no" << endl;}
else{
cout << "yes" << endl;}
}
}