Thread: Help solving this loop question

Hi all, i was having trouble solving this loop question,

Write a program that compute the series S
S=1-4+7-10+....+n (where n>10).

here is my work so far:

Code:

#include <stdio.h>
#include <conio.h>
main()
 {
int i,N,S;
printf("Please enter No. of terms");
scanf("%d",&N);
    if (N>10)
 {
float sign=1;
  for(i=0;i<N;i++)
S+=N*sign;
sign=sign*-1;
 }
printf(" the sum is : %d",S);
getch();
}

the program doesn't do what its supposed to do and it gives me a warning " sign is assigned a value that is never used" , i dont know what to do please help.

Curly braces aren't in the language just to look pretty. (That is: which statements are in your for loop? Which statements should be in your for loop?)

thanks for the help.