#include<iostream>
using namespace std;

int main() {
int n;
while (cin >> n){
int b,sum,avg; 
sum = 0; 
for (int i=0;i<n;i++){
cin >> b;
sum = sum + b;
}
avg = sum/n;
if (avg >=59){
cout << "no" << endl;
} else {
cout << "yes" << endl;
}
}
}

平均 > 59 不是 >=