Bruno and Fibonacci

    1#include <bits/stdc++.h>
    2using namespace std;
    3using ll = long long;
    4const int inf = 1e9;
    5const long long INF = 1e17; //❄️
    6int main() {
    7    ios::sync_with_stdio(0); cin.tie(0); 
    8    int n; string s; cin >> n >> s;
    9    unordered_set<int> pos;
    10    auto fib = [&](unordered_set<int> &p) {
    11        vector<int> dp(n + 1);
    12        p.insert(1);
    13        dp[1] = dp[2] = 1;
    14        for (int i = 3; i <= n; i++) {
    15            dp[i] = dp[i - 1] + dp[i - 2];
    16            if (dp[i] > n) break;
    17            p.insert(dp[i]);
    18        }
    19    };
    20    fib(pos);
    21    for (int i = 0; i < s.size(); i++) {
    22        if ((!pos.count(i + 1) && s[i] == 'A') || (pos.count(i + 1) && s[i] != 'A')) {
    23            cout << "Bruno, GO TO SLEEP" << '\n';
    24            return 0;
    25        }
    26    }
    27    cout << "That's quite the observation!" << '\n';
    28    return 0;
    29}