TOI11: กุลีแห่งท่าเรือ (Labor at the Deck)

#include<iostream>
using namespace std;
typedef long long int ll;
ll n,m,co[1000010],mn=2e9;

ll find(ll x){
    ll box=0;
    for(int i=1;i<=m;i++){
        box+=x/co[i];
    }
    return box;
}

int main(){
   scanf("%lld %lld",&m,&n);

   for(int i=1;i<=m;i++){
       scanf("%lld",&co[i]);
       mn=min(mn,co[i]);
   }
   ll f=mn,l=mn*n,ans=2e12;
   while(f<=l){
       ll mid=(f+l)/2;
       if(find(mid)>=n){
           l=mid-1;
           ans=min(ans,mid);
       }
       else{
           f=mid+1;
       }
   }
    printf("%lld",ans);
    return 0;
}