Bitwise Or vs LCM(牛客)

#include<bits/stdc++.h>
using namespace std;
const int N=2e5+10,M=1e6+10;
int a[N],n, b[M],ans1,ans2;
int main()
{

    cin>>n;
    for(int i=1;i<=n;i++)
    {
        cin>>a[i];
        if(b[a[i]]){cout<<min(b[a[i]],i)<<' '<<max(b[a[i]],i);return 0;}
        else b[a[i]]=i;
    }
    for(int i=1;i<=1e6;i++)if(b[i])
    {
        for(int j=i<<1;j<=1e6;j+=i)
        {
            if(b[j]){cout<<min(b[i],b[j])<<' '<<max(b[j],b[i]);return 0;}
        }
    }
    cout<<-1;
}