#include <iostream>  
using namespace std;  
int main()  
{  
int o,t1,t2,t3,t4,a,b,c,poeni,prosek;
cin>>o;
cin>>t1>>t2>>t3>>t4;

if(o==2){
poeni=60;
}
if(o==3){
poeni=70;
}
if(o==4){
poeni=80;
}
if(o==5){
poeni=90;
}


for(int i=0;i<=100;i++){
    
prosek=(t1+t2+t3+t4+i)/5;
if(prosek>=poeni){
    cout<<i<<endl;
    return 0;
}
}

cout<<"GRESHKA"<<endl;



    return 0;
}