485D - Maximum Value - CodeForces Solution

 
//#Chetan Patil [[email protected]]  [+919503368362]

#include<bits/stdc++.h>
using namespace std;
 
typedef  long long int  ll;

#define pi(x) cout<<x;
#define ps(x) cout<<x<<" ";
#define pnl(x) cout<<x<<"\n";
#define for0(n) for(i=0;i<n;i++)
#define for1(n) for(i=1;i<=n;i++)
#define m(x) memset(x,0,sizeof x);
#define nl cout<<"\n";
#define mp make_pair
#define pb push_back
#define fr first
#define se second
#define Inf 1e16


int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);                                                                                             
ll test,h,i,j,xy,flag=0,n,p,q,u,d,count,o1=0,o2=0,o3,e,l,r,x,y,m,z,max1,x1,y1,k,x2,y2,z1,z2,sum;
cin>>n;
vector<ll>a(2000002,0),left,right;
left=right=a;
for(i=0;i<n;i++){
    cin>>x;
    left[x]=x;
}
right=left;
for(i=1;i<=2000000;i++){
    if(left[i]==0){
        left[i]=left[i-1];
    }
}
max1=0;
for(i=1;i<=2000000;i++){
    if(left[i]==i){
        for(j=i;j<=2000000;j+=i){
            if(left[j-1]>=i){
                max1=max(left[j-1]%i,max1);
            }
        }
    }
}


cout<<max1<<"\n";
return 0;
}