diff --git a/100_Numpy_exercises_with_solutions.md b/100_Numpy_exercises_with_solutions.md
index 5f40a6a..12c658a 100644
--- a/100_Numpy_exercises_with_solutions.md
+++ b/100_Numpy_exercises_with_solutions.md
@@ -682,7 +682,8 @@ print(F)
 
 w,h = 16,16
 I = np.random.randint(0,2,(h,w,3)).astype(np.ubyte)
-F = I[...,0]*256*256 + I[...,1]*256 +I[...,2]
+# The parenthesis around 256*256 ensure the dtpye promoted to uint32 properly.Otherwise the first term will overflow.
+F = I[...,0]*(256*256) + I[...,1]*256 +I[...,2]
 n = len(np.unique(F))
 print(np.unique(I))
 ```
@@ -1179,4 +1180,4 @@ idx = np.random.randint(0, X.size, (N, X.size))
 means = X[idx].mean(axis=1)
 confint = np.percentile(means, [2.5, 97.5])
 print(confint)
-```
\ No newline at end of file
+```