#pragma GCC optimize("O5,unroll-loops,inline,fast-math") #pragma GCC target("avx2,bmi,bmi2,popcnt,lzcnt") #include <bits/stdc++.h> #define int long long #define exoworldgd cin.tie(0)->sync_with_stdio(0), cout.tie(0) using namespace std; const int N=3e5+5; int n,m,a[N],b[N],l=0,r=1e18,ans=0; signed main(void) { exoworldgd; cin >> n >> m; for(int i=0;i<n;i++) cin >> a[i]; for(int i=0;i<n;i++) cin >> b[i]; while(l<=r){ int mid=(l+r)>>1, ex=0,ok=0,need[n]; for (int i=0,x; i< n; i++) x=(mid+a[i]-1)/a[i], x=min(x,m), ex+=m-x, need[i]=mid-x*a[i]; for (int i=0; i< n;i++) { if (need[i]<=0) continue; int c=(need[i]+b[i]-1)/b[i]; if (c>ex) {ok=1; break;} ex-=c; } ok ? r=mid-1 : (ans=mid+1, l=mid+1); } cout << ans; }