View Code of Problem 71

#include <stdio.h>

int main ()
{
	int n;
	double sum = 0;
	scanf ("%d", &n);
	
	if (n == 1)
		printf ("2.00\n");
	else if (n == 2)
		printf ("3.50\n");
	else
	{
		int a1 = 1, a2 = 2;
		
		for (int i=3; i<=n; i++)
		{
			sum += (a1 + a2 + a2) / (1.0 * a2 + a1);
		}
		printf ("%.2f\n", sum + 3.5);
	}
	
	return 0;
}