#include <stdio.h>

int main(void)
{
	const int n = 10;
	int a[n], count = 0;
	float sum = 0;
	
	for (int i = 0; i < n; i++)
		scanf("%d", &a[i]);

	for (int i = 0; i < n; i++)
		if (a[i] < 0)
		{
			count++;
			sum += a[i];
		}

	float res = sum/count;
	printf("%f\n", res);

	return 0;
}