#include<iostream> #include<cstdio> using namespace std; int main(){ double b=0; int n,i; cin>>n; int a[n-1]={0}; while(i<=n){ if(i==n-1){ break; } cin>>a[i]; i++; } i=0; while(i<=n-1){ if(i==n){ break; } b=b+a[i]; i++; } printf("%.2f",b/(n-1)); return 0; }