It is impossible directly to find a prime number p,q of a large semiprime n = pq using Trial Division method. So the most of the factorization algorithms use the indirection method which finds a prime number of p = GCD(a-b, n), q=GCD(a+b, n); get with a congruence of squares of $a^2{equiv}b^2$ (mod n). It is just known the fact which the area that selects p and q about n=pq is between $10{cdots}00$ < p < $sqrt{n}$ and $sqrt{n}$ < q < $99{cdots}9$ based on $sqrt{n}$ in the range, [$10{cdots}01$, $99{cdots}9$] of $l(p)=l(q)=l(sqrt{n})=0.5l(n)$. This paper proposes the method that reduces the range of p using information obtained from n. The proposed method uses the method that sets to $p_{min}=n_{LR}$, $q_{min}=n_{RL}$; divide into $n=n_{LR}+n_{RL}$, $l(n_{LR})=l(n_{RL})=l(sqrt{n})$. The proposed method is more effective from minimum 17.79% to maxmimum 90.17% than the method that reduces using $sqrt{n}$ information.