From ac1325e6eee9ccff046085735d61aa969dc09b75 Mon Sep 17 00:00:00 2001
From: E7-87-83 <fungcheokyin@gmail.com>
Date: Sun, 15 Aug 2021 10:02:48 +0800
Subject: improve bound on ch-1.pl

---
 challenge-125/cheok-yin-fung/perl/ch-1.pl | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/challenge-125/cheok-yin-fung/perl/ch-1.pl b/challenge-125/cheok-yin-fung/perl/ch-1.pl
index 6258feda8a..7a700d2ed0 100644
--- a/challenge-125/cheok-yin-fung/perl/ch-1.pl
+++ b/challenge-125/cheok-yin-fung/perl/ch-1.pl
@@ -37,6 +37,11 @@ sub pyth ($n) {
         }
     }
 
+
+    # (C+1)^2 - C^2 = 2C + 1
+    # 2C + 1 <= n^2
+    # C <= (n^2-1)/2
+
     for my $b0 ($n+1..int ($n*$n-1)/2) {
         my $is_sq = $b0*$b0 + $n*$n;
         if (sqrt($is_sq) == int sqrt($is_sq)) {
-- 
cgit