#include <stdio.h>
#include <windows.h>

#define _EULER1 1

double euler(int n) {
	double	result = 0.0;
	for(int i = 1; i < n; i++)
		result += 1.0 / (double)i;
	return result;
}

double euler2(int n) {
	double	result1 = 0.0;
	double	result2 = 0.0;
	for(int i = 1; i < n; i += 2) {
		result1 += 1.0 / (double)i;
		result2 += 1.0 / (double)(i + 1);
	}
	if(n % 2)		//odd
		return result1 + result2 + 1.0 / (double)n;
	else			//even
		return result1 + result2;
}

void main(void) {
	int		t;
	t = GetTickCount();
#ifdef _EULER1
	printf("%f\n", euler(1000000000));
#else
	printf("%f\n", euler2(1000000000));
#endif
	printf("%dms\n", GetTickCount() - t);
}