diff --git a/TangDou/Topic/SpareTire.cpp b/TangDou/Topic/SpareTire.cpp
index 1d3e39e..86541ca 100644
--- a/TangDou/Topic/SpareTire.cpp
+++ b/TangDou/Topic/SpareTire.cpp
@@ -59,17 +59,18 @@ signed main() {
                     s *= p[j];
                 }
 
-            int nn = n / s;
-            int pt = (nn) % mod * (nn + 1) % mod * (2 * nn + 1) % mod * Six % mod;
+            // 这里没看懂
+            int k = n / s;
+            int pt = (k) % mod * (k + 1) % mod * (2 * k + 1) % mod * Six % mod;
             pt = pt * s % mod * s % mod;
-            pt = (pt + nn * (s + s * nn) % mod * Two % mod) % mod;
-            
+            pt = (pt + k * (s + s * k) % mod * Two % mod) % mod;
+
             if (cnt & 1)
                 res = (res - pt + mod) % mod;
             else
                 res = (res + pt) % mod;
         }
-        // 补集，标准取模动作
+        // 输出
         cout << res << endl;
     }
 }