#include <stdio.h>
#include <stdlib.h>
int main()
{
int i;
double tmp = 1, sum = 0, flag = 1;
for (i = 1; i <= 100; i++)
{
tmp = 1.0 / i * flag;//(i % 2 ? 1 : -1);
sum += tmp;
flag *= -1;
}
printf("%lf\n", sum);
system("pause");
return 0;
}