#include<bits/stdc++.h> using namespace std; double n,m,p; int a[101]; int main(){ cin>>n; for(int i=1;i<=n;i++){ cin>>a[i]; m+=a[i]; } p=m/n; printf("%.1lf",p); cout<<endl; for(int i=1;i<=n;i++){ if(a[i]>=p) cout<<i<<":"<<a[i]<<" "; } return 0; }