#include <stdio.h>

int main (){

	int dist,soma=0,i;
	double r;
	char nome[200];

	while (scanf(" %[^\n]",nome) != EOF){

	scanf("%d",&dist);

	soma +=dist;

    i++;

	}

		r = soma/i;

	printf("%.1lf\n",r);

	return 0;
}