diff --git a/weeks/week-15/solutions/fychao/0603/gcd.py b/weeks/week-15/solutions/fychao/0603/gcd.py
new file mode 100644
index 000000000..bc06fbadd
--- /dev/null
+++ b/weeks/week-15/solutions/fychao/0603/gcd.py
@@ -0,0 +1,9 @@
+from math import gcd
+
+
+def sum_of_gcd(n: int) -> int:
+    total = 0
+    for i in range(1, n):
+        for j in range(i + 1, n + 1):
+            total += gcd(i, j)
+    return total
diff --git a/weeks/week-15/solutions/fychao/0603/test_gcd.py b/weeks/week-15/solutions/fychao/0603/test_gcd.py
new file mode 100644
index 000000000..45b0278d5
--- /dev/null
+++ b/weeks/week-15/solutions/fychao/0603/test_gcd.py
@@ -0,0 +1,18 @@
+import unittest
+
+from gcd import sum_of_gcd
+
+
+class TestSumOfGcd(unittest.TestCase):
+    def test_n_equals_2(self):
+        self.assertEqual(sum_of_gcd(2), 1)
+
+    def test_n_equals_10(self):
+        self.assertEqual(sum_of_gcd(10), 67)
+
+    def test_n_equals_1_edge_case(self):
+        self.assertEqual(sum_of_gcd(1), 0)
+
+
+if __name__ == "__main__":
+    unittest.main()