#include <bits/stdc++.h> #define FOR(i,b,e) for(int i=(b); i <= (e); ++i) #define FORD(i,b,e) for(int i=(b); i >= (e); --i) #define SIZE(c) (int) (c).size() #define FORE(i,c) FOR(i,0,SIZE(c)-1) #define pb push_back using namespace std; typedef long long ll; typedef vector <int> VI; typedef vector <ll> VL; /*************************************************************************/ const int MAXL = 200000; int sRes = 0; ll res[MAXL]; VL calcUbs(ll n, VI &primes) { VL ubs(primes.size()); FORE(i,primes) { ubs[i] = n / primes[i]; } return ubs; } /*************************************************************************/ ll ans = 1; void memProds(int i, const VI &primes, const VL &ubs, ll curr, ll n) { if (i == primes.size()) { res[sRes++] = curr; return; } while (true) { memProds(i + 1, primes, ubs, curr, n); if (curr > ubs[i]) break; curr *= primes[i]; } } void solveProds(int i, const VI &primes, const VL &ubs, ll curr, ll n) { if (i == primes.size()) { if (curr <= (n >> 1)) { int ind = upper_bound(res, res + sRes, n / curr) - res; if (ind > 0) { ans = max(ans, curr * res[ind - 1]); } } else { ans = max(ans, curr); } return; } while (true) { solveProds(i + 1, primes, ubs, curr, n); if (curr > ubs[i]) break; curr *= primes[i]; } } /*************************************************************************/ int main() { ios_base::sync_with_stdio(0); int k; ll n; cin >> k >> n; VI primes(k); FOR(i,0,k-1) { cin >> primes[i]; } sort(primes.begin(), primes.end()); const int MAXLEFT = 8; int leftLen = min(MAXLEFT, k / 2); int rightLen = k - leftLen; VI memPart(primes.begin(), primes.begin() + leftLen); VI solvePart(primes.begin() + leftLen, primes.end()); ll nSqrt; ll lSqrt = 0, rSqrt = 1000000001; while (rSqrt - lSqrt > 1) { ll mid = (lSqrt + rSqrt) / 2; if (mid * mid < n) { lSqrt = mid; } else { rSqrt = mid; } } nSqrt = rSqrt; FOR(_,0,1) { sRes = 0; memProds(0, memPart, calcUbs(nSqrt, memPart), 1, nSqrt); sort(res, res + sRes); solveProds(0, solvePart, calcUbs(n, solvePart), 1, n); swap(memPart, solvePart); } cout << ans; 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 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 | #include <bits/stdc++.h> #define FOR(i,b,e) for(int i=(b); i <= (e); ++i) #define FORD(i,b,e) for(int i=(b); i >= (e); --i) #define SIZE(c) (int) (c).size() #define FORE(i,c) FOR(i,0,SIZE(c)-1) #define pb push_back using namespace std; typedef long long ll; typedef vector <int> VI; typedef vector <ll> VL; /*************************************************************************/ const int MAXL = 200000; int sRes = 0; ll res[MAXL]; VL calcUbs(ll n, VI &primes) { VL ubs(primes.size()); FORE(i,primes) { ubs[i] = n / primes[i]; } return ubs; } /*************************************************************************/ ll ans = 1; void memProds(int i, const VI &primes, const VL &ubs, ll curr, ll n) { if (i == primes.size()) { res[sRes++] = curr; return; } while (true) { memProds(i + 1, primes, ubs, curr, n); if (curr > ubs[i]) break; curr *= primes[i]; } } void solveProds(int i, const VI &primes, const VL &ubs, ll curr, ll n) { if (i == primes.size()) { if (curr <= (n >> 1)) { int ind = upper_bound(res, res + sRes, n / curr) - res; if (ind > 0) { ans = max(ans, curr * res[ind - 1]); } } else { ans = max(ans, curr); } return; } while (true) { solveProds(i + 1, primes, ubs, curr, n); if (curr > ubs[i]) break; curr *= primes[i]; } } /*************************************************************************/ int main() { ios_base::sync_with_stdio(0); int k; ll n; cin >> k >> n; VI primes(k); FOR(i,0,k-1) { cin >> primes[i]; } sort(primes.begin(), primes.end()); const int MAXLEFT = 8; int leftLen = min(MAXLEFT, k / 2); int rightLen = k - leftLen; VI memPart(primes.begin(), primes.begin() + leftLen); VI solvePart(primes.begin() + leftLen, primes.end()); ll nSqrt; ll lSqrt = 0, rSqrt = 1000000001; while (rSqrt - lSqrt > 1) { ll mid = (lSqrt + rSqrt) / 2; if (mid * mid < n) { lSqrt = mid; } else { rSqrt = mid; } } nSqrt = rSqrt; FOR(_,0,1) { sRes = 0; memProds(0, memPart, calcUbs(nSqrt, memPart), 1, nSqrt); sort(res, res + sRes); solveProds(0, solvePart, calcUbs(n, solvePart), 1, n); swap(memPart, solvePart); } cout << ans; return 0; } /*************************************************************************/ |