#include <stdio.h>

int main(void)
{
    float arr[5] = {0};
    float sum = 0;
    int i = 0;
    for(i = 0; i < 5; i++)
    {
        scanf("%f", &arr[i]);
        sum += arr[i];
    }
    printf("%.2f\n", sum/5);
    return 0;
}