#include<stdio.h>
int main(){
    int size,i;
    float avg;
    float sum=0.0;
    scanf("%d",&size);
    int mark[10];
    for(i=0;i<size;i++){
        scanf("%d",&mark[i]);
        if(mark[i]<0){
            printf("Invalid input");
            return 0;
            
        }
    }
    for(I=0;i<size;i++){
    sum=sum+mark[i];
    
}
avg=sum/size;
printf("%.2f",avg);
}