/* quick and dirty check for common factor with n */
public bool cfactor(int s)
{
int r, n = length;
int g;
FF x = new FF(n);
FF y = new FF(n);
y.set(s);
x.copy(this);
x.norm();
do
{
x.sub(y);
x.norm();
while (!x.iszilch() && x.parity() == 0)
{
x.shr();
}
} while (comp(x, y) > 0);
g = (int)x.v[0].get(0);
r = igcd(s, g);
if (r > 1)
{
return(true);
}
return(false);
}