F - Modulo

https://codeforces.com/gym/103860/submission/167192783

Gym/103860/F/F.cpp

@@ -0,0 +1,53 @@
+#include <iostream>
+#include <algorithm>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 22;
+
+int n;
+long long a[N], x, ans;
+bool vis[N];
+
+void dfs(int idx, long long now, int cnt) {
+    if (now < ans) return;
+    if (cnt == n || now < a[1]) {
+        ans = std::max(ans, now);
+
+        return;
+    }
+
+    vis[idx] = true;
+
+    for (int i = 1; i <= n; i++) {
+        if (now < a[i]) break;
+        if (vis[i]) continue;
+
+        dfs(i, now % a[i], cnt + 1);
+    }
+
+    vis[idx] = false;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> a[i];
+    }
+
+    cin >> x;
+
+    std::sort(a + 1, a + 1 + n);
+
+    dfs(0, x, 0);
+
+    cout << ans << endl;
+
+    return 0;
+}