From 211b5e0172c20bc34e5af9ab5b64477331c0fdb8 Mon Sep 17 00:00:00 2001
From: mingda <leimingda@pku.edu.cn>
Date: Fri, 15 Jan 2021 22:45:33 +0800
Subject: [PATCH] fix _SolveQuadraticFunctionForTrade sub error

---
 contracts/lib/DODOMath.sol | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/contracts/lib/DODOMath.sol b/contracts/lib/DODOMath.sol
index a847f60..e3239ac 100644
--- a/contracts/lib/DODOMath.sol
+++ b/contracts/lib/DODOMath.sol
@@ -165,10 +165,10 @@ library DODOMath {
 
         bool bSig;
         if (bAbs >= part2) {
-            bAbs = bAbs.sub(part2);
+            bAbs = bAbs - part2;
             bSig = false;
         } else {
-            bAbs = part2.sub(bAbs);
+            bAbs = part2 - bAbs;
             bSig = true;
         }
         bAbs = bAbs.div(DecimalMath.ONE);
@@ -190,6 +190,11 @@ library DODOMath {
             numerator = bAbs.add(squareRoot);
         }
 
-        return V1.sub(DecimalMath.divCeil(numerator, denominator));
+        uint256 V2 = DecimalMath.divCeil(numerator, denominator);
+        if (V2 > V1) {
+            return 0;
+        } else {
+            return V1 - V2;
+        }
     }
 }