diff --git a/Luogu/problem/P3742/P3742.cpp b/Luogu/problem/P3742/P3742.cpp
new file mode 100644
index 00000000..ec33253e
--- /dev/null
+++ b/Luogu/problem/P3742/P3742.cpp
@@ -0,0 +1,18 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int main() {
+    int n;
+    string s1, s2, g;
+    cin >> n >> s1 >> s2;
+    for (int i = 0; i < n; i++) {
+        g.push_back(min(s1[i], s2[i]));
+        if (s1[i] < s2[i]) {
+            cout << -1 << endl;
+            return 0;
+        }
+    }
+    cout << g << endl;
+    return 0;
+}