#include <stdio.h>

double sum(int n);

main()
{
	printf("%g\n", sum(5));
}	

double sum(int n)
{
	double s;
	
	if (n == 1)
		return (1);
	else	
	{
		s = 1./(n * n) + sum(n-1);
       	
		return (s);
	}
}