#include<stdio.h>
float ave4(float a, float b, float c, float d)
{
	float ans=a+b+c+d;
	return ans/4.0;
}

main()
{
	float x,y,z,p;
	printf(" input x= "); scanf("%f",&x);
	printf(" input y= "); scanf("%f",&y);
	printf(" input z= "); scanf("%f",&z);
	printf(" input p= "); scanf("%f",&p);
	printf("\n ave4 = %f\n",ave4(x,y,z,p));
}