Sum in C cannot solve -

ok,so wrote program , compiled it. it's ok, when run in windows 7 get's me error c0000005. have no idea why.

overview of program

i want program give me sum of numbers depends of given "n" : 1-1x3+1x3x5-...+-1x3x5x...x(2*n-1).

please me,i begginer.

#include <stdio.h> #include <conio.h>  int main() {   int n, sum=0, i, signum;   printf("give n: ");   scanf("%d", n);   for(i=1, signum=1; i-(2*n-1); sum+=(signum*(sum*i)),i+2,signum=-signum)     ;   printf("sum is: %d", sum);   getch();   return 0; } 

you write code this, think lot clearer.

#include <stdio.h>  int main() {     int i, n, sum = 1, term = 1;     printf("give n: ");     scanf("%d", &n);             // address of n     (i = 2; <= n; ++i) {   // simple loop         term *= -(2 * - 1);    // multiply previous , flip sign         sum += term;     }     printf("sum is: %d", sum);     return 0; } 

i'm on linux, removed header <conio.h> non-standard.