#include <bits/stdc++.h>
using namespace std;
int main()
{
	int sum=0;
	float AVE;
	int n;
	cin>>n;
	int a[n];
	for(int i=0;i<n;i++){
		cin>>a[i];
	}
	for(int i=0;i<n;i++){
		sum+=a[i];
	}
	AVE=(sum*1.0)/n;
	printf("%.1f\n",AVE);
	for(int i=0;i<n;i++){
		if(a[i]>AVE){
			cout<<i+1<<":"<<a[i]<<" ";
		}
	}	
	
return 0;

}

/**************************************************************
	Problem: 1155
	User: mc002
	Language: C
	Result: Compile Error
****************************************************************/