#include <iostream>

using namespace std;

int main(){

int n;

while(cin>>n){

int grade,total;

for(int i=0;i<n;i++){

cin>>grade;

total+=grade;

}

if(total<=59*n){

cout<<"yes"<<endl;

}

else{

cout<<"no"<<endl;

  }

}

 return 0;    

}

int grade,total;

total沒有初始化