#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>


int main()
{
        int dist , i=0 , soma=0;
        double media;
        char nome[30];
        while(gets(nome) != NULL && scanf("%d ",&dist) != EOF)
        {
                soma += dist;
                i++;
        }
        media = soma / (double)i;
        printf("%.1f\n" , media);
        return 0;
}