// 01001100 01001111 01010100 01000001 \\ // \\ // ╦ ╔═╗╔╦╗╔═╗ \\ // ║ ║ ║ ║ ╠═╣ \\ // ╩═╝╚═╝ ╩ ╩ ╩ \\ // \\ // 01001100 01001111 01010100 01000001 \\ #include <bits/stdc++.h> using namespace std; #define nl '\n' #define ff first #define ss second #define ll long long #define ld long double #define terminator main #define pll pair<ll,ll> #define add insert #define append push_back #define pii pair<int,int> #define all(x) (x).begin(),(x).end() #define L0TA ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL) const int N = 3e5 + 6; ll n, m; ll a[N]; ll b[N]; bool check(ll x){ ll p, q, r; p = q = 0; for(int i = 0; i < n && p < n * m; i++){ r = (x + a[i] - 1) / a[i]; if(r > m){ r = (x - a[i] * m + b[i] - 1) / b[i]; p += r; } else if(r < m) q += m - r; } if(p > q) return 0; return 1; } void solve(){ cin >> n >> m; for(int i = 0; i < n; i++) cin >> a[i]; for(int i = 0; i < n; i++){ cin >> b[i]; a[i] = max(a[i], b[i]); } ll ans = 0; for(ll i = 576460752303423488; i > 0; i /= 2) if(check(ans + i)) ans += i; cout << ans; } int terminator(){ L0TA; int T = 1; //cin >> T; while(T--) solve(); return 0; }