#include <bits/stdc++.h> using namespace std; void move_inside(int); void move_outside(int); int press_button(); int min_cardinality(int N) { vector<int> types(N, -1); int t = 0; for (int i = 0; i < N; i++) { if (types[i] != -1) continue; types[i] = t; move_inside(i); for (int j = i + 1; j < N; j++) { move_inside(j); int ret = press_button(); if (ret > 1) types[j] = t; move_outside(j); } t++; } vector<int> cnt(t); for (int i = 0; i < N; i++) cnt[types[i]]++; int mn = cnt[0]; for (auto x : cnt) if (x < mn) mn = x; return mn; }