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