add aloha/2025hcpc

storage/aloha/cpp/2025hcpc-div1-F.cpp

@@ -0,0 +1,11 @@
+#include <malloc.h>
+#include <stdint.h>
+#include <stdio.h>
+
+int main() {
+    uint64_t n;
+
+    scanf("%d", &n);
+    double p = (n - 1) * (n) / (double) 4;
+    printf("%f\n", p);
+}