太抽象了

#include <bits/stdc++.h>
using namespace std;

int main() {
    int n;
    cin >> n;
    vector<int> arr(n);
    for (int i = 0; i < n; ++i) {
        cin >> arr[i];
    }
    set<int> unique_set;
    vector<int> month = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    vector<int> month_checked(12, 0);

    for (int i = 0; i < n - 7; ++i) {
        if (arr[i] == 2) {
            for (int j = i + 1; j < n - 6; ++j) {
                if (arr[j] == 0) {
                    for (int k = j + 1; k < n - 5; ++k) {
                        if (arr[k] == 2) {
                            for (int l = k + 1; l < n - 4; ++l) {
                                if (arr[l] == 3) {
                                    for (int a = l + 1; a < n - 3; ++a) {
                                        if (arr[a] < 2) {
                                            for (int b = a + 1; b < n - 2; ++b) {
                                                int month1 = arr[a] * 10 + arr[b];
                                                if (0 < month1 && month1 < 13 && month_checked[month1 - 1] == 0) {
                                                    month_checked[month1 - 1] = 1;
                                                    for (int c = b + 1; c < n - 1; ++c) {
                                                        if (arr[c] < 4) {
                                                            for (int d = c + 1; d < n; ++d) {
                                                                int day1 = arr[c] * 10 + arr[d];
                                                                if (0 < day1 && day1 <= month[month1 - 1]) {
                                                                    unique_set.insert(arr[a] * 1000 + arr[b] * 100 + arr[c] * 10 + arr[d]);
                                                                }
                                                            }
                                                        }
                                                    }
                                                }
                                            }
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }
    }

    cout << unique_set.size() << endl;
    return 0;
}