#include <iostream> #include <vector> #include <algorithm> using namespace std; vector<int> primes; long long n; int k; long long findRec(long long current = 1, int index = 0) { if (current >= n) return 0; if (current < 0) return 0; long long res = current; for (int i = index; i < k; ++i) { res = max(res, findRec(current * primes[i], i)); } return res; } long long find() { if (k == 1) { long long res = 1; while (res <= n) res *= primes[0]; return res / primes[0]; } while (n) { long long copy = n; int index = 0; while (copy > 1 && index < k) { while (copy %primes[index] == 0) copy /= primes[index]; ++index; } if (copy == 1) return n; --n; } } int main() { ios_base::sync_with_stdio(0); cin.tie(0); cin >> k >> n; int mini = 101; primes.resize(k); for (int i = 0; i < k; ++i) { cin >> primes[i]; mini = min(mini, primes[i]); } if (k < 5 || (mini > 10 && k < 6)) cout << findRec(); else if (n < 10000000) cout << find(); else cout << findRec(); return 0; }
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 | #include <iostream> #include <vector> #include <algorithm> using namespace std; vector<int> primes; long long n; int k; long long findRec(long long current = 1, int index = 0) { if (current >= n) return 0; if (current < 0) return 0; long long res = current; for (int i = index; i < k; ++i) { res = max(res, findRec(current * primes[i], i)); } return res; } long long find() { if (k == 1) { long long res = 1; while (res <= n) res *= primes[0]; return res / primes[0]; } while (n) { long long copy = n; int index = 0; while (copy > 1 && index < k) { while (copy %primes[index] == 0) copy /= primes[index]; ++index; } if (copy == 1) return n; --n; } } int main() { ios_base::sync_with_stdio(0); cin.tie(0); cin >> k >> n; int mini = 101; primes.resize(k); for (int i = 0; i < k; ++i) { cin >> primes[i]; mini = min(mini, primes[i]); } if (k < 5 || (mini > 10 && k < 6)) cout << findRec(); else if (n < 10000000) cout << find(); else cout << findRec(); return 0; } |