#include<bits/stdc++.h> using namespace std; int n,ans; double h[110],avg; int main(){ cin>>n; for(int i=1;i<=n;i++){ cin>>h[i]; avg+=h[i]; } avg/=n; printf("0.1lf\n",avg); for(int i=1;i<=n;i++){ if(h[i]>avg) printf("%d:%.0lf ",i,h[i]); } return 0; }