diff --git a/30xxx/30878.cpp b/30xxx/30878.cpp
new file mode 100644
index 00000000..7166121c
--- /dev/null
+++ b/30xxx/30878.cpp
@@ -0,0 +1,23 @@
+#include <iostream>
+using namespace std;
+
+int gcd(int a, int b) {
+  return b ? gcd(b, a % b) : a;
+}
+
+void solve(void) {
+  int m; cin >> m;
+
+  int a = m * m * (90 - m);
+  int b = 108000;
+  int g = gcd(a, b);
+  cout << a / g << "/" << b / g;
+}
+
+int main(void) {
+  ios::sync_with_stdio(false);
+  cin.tie(nullptr);
+
+  solve();
+  return 0;
+}
\ No newline at end of file