#include<bits/stdc++.h> using namespace std; int a[2200]; int main(){ int n,k=0,b=0,c=0,d=0; cin>>n; for(int i=1;i<=n;i++){ cin>>a[i]; if(a[i]<=18)k++; else if(a[i]>18 && a[i]<=35)b++; else if(a[i]>35 && a[i]<=60)c++; else if(a[i]>60)d++; } printf("%.2lf%\n",k*1.0/n*100); return 0; }