OJ Board

I am getting presentation error.But can't understand why.please help me out.

#include<stdio.h>
#include<math.h>

int main(void)
{
int a[1001];
int i,j,n,k,c,m,q,r;
while(scanf("%d%d",&n,&c)==2)
{
k=0;
a[0]=0;
a[1]=1;
for(i=2;i<=n;i++)
{
a =1;
}
for(i=2;i<=sqrt(n);i++)
{
if(a ==0 ...