Hi all would appreciate some help or general advice on changing the following code so as to stop whenever i>sqrt(n). My problem is that n is a integer input from a user so how do I calculate a sqrt of it?

Thanks in advance

Andrew

Code:
/*Is n a prime?*/

main()
{
int i,m,n;
m=0;
scanf("%d", &n);
for (i=2;i<n;i++){
      if (n%i==0)
      m=1;
}
if (m==0)
    printf("%d is prime",n);
else
    printf("%d is not prime",n);
return 0;
}