#include <stdio.h>


int main(void)
{
	int s[6];
	int total = 0;
	int tmp;
	int i, j;

	scanf("%d %d %d %d %d %d", &s[0], &s[1], &s[2], &s[3], &s[4], &s[5]);

	for (i = 5; i > 0; i--) {
		for (j = 0; j < i; j++) {
			if (s[j] > s[j + 1]) {
				tmp = s[j];
				s[j] = s[j + 1];
				s[j + 1] = tmp;
			}
		}
	}
	
	for (i = 1; i < 5; i++) {
		total += s[i];
	}

	printf("%.2f\n", (double)total / 4);

	return 0;
}