/* 1 zadatak... (c) kreator */
#include <stdio.h>
#include <math.h>

void main(void)
{
	int i,n;
	float sum=0.;
	printf("Unesi broj clanova n ");
	scanf("%d", &n);
	for(i=2;i<=n;++i) sum+=1/(float)((i-1)*(i+1));
	printf("Dobiveno %f, stvarno %f, aps. pogreska je %f\n", 
		sum, 3/4., fabs(sum-3/4.));
}