#include<iostream> int main(){ double z=0,p,r; scanf("%lf",&r); int a[101]={0}; for(int i;i<=r;i++){ scanf("%d",&a[i]); z+=a[i]; } p=z/r; printf("%.1lf\n",p); for(int i;i<=r;i++){ if(a[i]>p) printf("%d:%d ",i,a[i]); } return 0; }