#include<stdio.h>
#include<conio.h>
int main()
{
int i, n;
float S;
S = 0;
do
{
printf("\nNhap n: ");
scanf("%d", &n);
if(n < 1)
{
printf("\nN phai lon hon hoac bang 1. Xin nhap lai !");
}
}while(n < 1);
for(i = 1; i <= n; i++)
{
S = S + 1.0 / (2 * i);
}
printf("\nTong la: %f", S);
getch();
return 0;
}