diff --git a/AcWing/203/203.cpp b/AcWing/203/203.cpp
new file mode 100644
index 00000000..6717c7e9
--- /dev/null
+++ b/AcWing/203/203.cpp
@@ -0,0 +1,32 @@
+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+int a, b, x, y;
+
+int exgcd(int a, int b, int &x, int &y) {
+    if (!b) {
+        x = 1;
+        y = 0;
+        return a;
+    }
+
+    int g = exgcd(b, a % b, y, x);
+    y -= a / b * x;
+
+    return g;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+
+    cin >> a >> b;
+
+    exgcd(a, b, x, y);
+
+    cout << (x % b + b) % b << endl;
+
+    return 0;
+}