diff --git a/S2OJ/1851/1851.cpp b/S2OJ/1851/1851.cpp
new file mode 100644
index 00000000..ca7d1978
--- /dev/null
+++ b/S2OJ/1851/1851.cpp
@@ -0,0 +1,69 @@
+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e6 + 5;
+
+int n, q, cnt, tr[N][26], siz[N][26];
+long long f[26][26], res;
+
+void insert(std::string s) {
+    int cur = 0;
+
+    for (int i = 0; i < s.size(); i++) {
+        int x = s[i] - 'a';
+
+        if (!tr[cur][x]) {
+            tr[cur][x] = ++cnt;
+        }
+
+        for (int j = 0; j < 26; j++) {
+            if (!tr[cur][j] || j == x) continue;
+
+            f[x][j] += siz[cur][j];
+        }
+
+        siz[cur][x]++;
+        cur = tr[cur][x];
+    }
+
+    for (int i = 0; i < 26; i++) {
+        if (!tr[cur][i]) continue;
+
+        res += siz[cur][i];
+    }
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> q;
+
+    for (int i = 1; i <= n; i++) {
+        std::string s;
+
+        cin >> s;
+
+        insert(s);
+    }
+
+    while (q--) {
+        long long ans = 0;
+        std::string t;
+
+        cin >> t;
+
+        for (int i = 0; i < 26; i++) {
+            for (int j = i + 1; j < 26; j++) {
+                ans += f[t[i] - 'a'][t[j] - 'a'];
+            }
+        }
+
+        cout << ans + res << endl;
+    }
+
+    return 0;
+}