S - Odd Numbers of Divisors

#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;
vector<ll> divisors[1000005];
int mark[10000]={0};
void Divisor(ll n)
{
    for(ll i=1;i<=n;i++)
    {
        for(ll j=i;j<=n;j+=i)divisors[j].push_back(i);
    }
    return;
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    #ifndef ONLINE_JUDGE
    freopen("input.cpp","r",stdin);
    #endif // ONLINE_JUDGE
    Divisor(1000000);
    for(int i=1;i<=1000000;i++)
    {
        if(divisors[i].size()%2==1)
        {
            //cout<<i<<" : "<<divisors[i].size()<<endl;
            mark[divisors[i].size()]++;
        }
    }
    for(int i=0;i<=10000;i++)if(mark[i])cout<<i<<" : "<<mark[i]<<endl;
    return 0;
}