diff --git a/25xxx/25090.cpp b/25xxx/25090.cpp
new file mode 100644
index 00000000..1573fd01
--- /dev/null
+++ b/25xxx/25090.cpp
@@ -0,0 +1,26 @@
+#include <algorithm>
+#include <iostream>
+#include <vector>
+using namespace std;
+
+void solve(int idx) {
+  int n; cin >> n;
+  vector<int> s(n);
+  for (int i=0; i<n; i++) cin >> s[i];
+  sort(s.begin(), s.end());
+
+  int ans = 0;
+  for (int i=0; i<n; i++) {
+    if (ans + 1 <= s[i]) ans++;
+  }
+  cout << "Case #" << idx << ": " << ans << "\n";
+}
+
+int main(void) {
+  ios::sync_with_stdio(false);
+  cin.tie(nullptr);
+
+  int t; cin >> t;
+  for (int i=1; i<=t; i++) solve(i);
+  return 0;
+}
\ No newline at end of file