#include<stdio.h>
 int main()
 {
     int n,ind;
     scanf("%d",&n);
     int arr[n];
     float sum,avg;
     for(ind =0;ind<n;ind++){
         if(scanf("%d",&arr[ind])!=1 || arr[ind]<0){
             printf("Invalid input");
             retuen 0;
         }
         sum+=arr[ind];
     }
 avg=sum/n;
 printf("%.2f",avg);
 return 0;
 }