diff --git a/TangDou/Topic/SpareTire.cpp b/TangDou/Topic/SpareTire.cpp
index 86541ca..ad949b8 100644
--- a/TangDou/Topic/SpareTire.cpp
+++ b/TangDou/Topic/SpareTire.cpp
@@ -59,9 +59,10 @@ signed main() {
                     s *= p[j];
                 }
 
-            // 这里没看懂
+            // 比如找到了s=6=2*3，需要知道s是奇数个，还是偶数个因子
+            // n/s:范围内6的倍数有多少个
             int k = n / s;
-            int pt = (k) % mod * (k + 1) % mod * (2 * k + 1) % mod * Six % mod;
+            int pt = k * (k + 1) % mod * (2 * k + 1) % mod * Six % mod;
             pt = pt * s % mod * s % mod;
             pt = (pt + k * (s + s * k) % mod * Two % mod) % mod;