diff --git a/Math/bigint.h b/Math/bigint.h
index f533f5a..6af524f 100644
--- a/Math/bigint.h
+++ b/Math/bigint.h
@@ -545,11 +545,11 @@ struct BigInt {
         return a.empty() || (a.size() == 1 && !a[0]);
     }
 
-    friend BigInt gcd(const BigInt &a, const BigInt &b) {
-        return b.isZero() ? a : gcd(b, a % b);
+    friend BigInt gcd(const BigInt &x, const BigInt &y) {
+        return y.isZero() ? x : gcd(y, x % y);
     }
-    friend BigInt lcm(const BigInt &a, const BigInt &b) {
-        return a / gcd(a, b) * b;
+    friend BigInt lcm(const BigInt &x, const BigInt &y) {
+        return x / gcd(x, y) * y;
     }
 
     friend BigInt sqrt(const BigInt &a1) {
diff --git a/Math/tests/yosupo_bigint_add.test.cpp b/Math/tests/yosupo_bigint_add.test.cpp
new file mode 100644
index 0000000..ac4f58d
--- /dev/null
+++ b/Math/tests/yosupo_bigint_add.test.cpp
@@ -0,0 +1,16 @@
+#define PROBLEM "https://judge.yosupo.jp/problem/addition_of_big_integers"
+
+#include "bits/stdc++.h"
+using namespace std;
+
+#include "../bigint.h"
+
+int main() {
+    ios::sync_with_stdio(0); cin.tie(0);
+    int ntest; cin >> ntest;
+    while (ntest--) {
+        BigInt a, b; cin >> a >> b;
+        cout << a + b << endl;
+    }
+    return 0;
+}