From bd2608270532b3dc85576ca22d691c935484675a Mon Sep 17 00:00:00 2001
From: mingda <leimingda@pku.edu.cn>
Date: Wed, 8 Jul 2020 17:59:57 +0800
Subject: [PATCH] [audit]#8 handle sqrt coner case

---
 contracts/lib/SafeMath.sol | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/contracts/lib/SafeMath.sol b/contracts/lib/SafeMath.sol
index 92eb396..8454b3a 100644
--- a/contracts/lib/SafeMath.sol
+++ b/contracts/lib/SafeMath.sol
@@ -53,7 +53,7 @@ library SafeMath {
     }
 
     function sqrt(uint256 x) internal pure returns (uint256 y) {
-        uint256 z = (x + 1) / 2;
+        uint256 z = add(x, 1) / 2;
         y = x;
         while (z < y) {
             y = z;