Multiset_OOP

class Multiset
{
    public:
    int n,aib[1000001];
    Multiset(int n)
    {
        this->n=n;
        for(int i=0;i<=n;++i)
            aib[i]=0;
    }

    void Insert(int x)
    {
        for(int i=x;i<=n;i+=(i&-i))
            ++aib[i];
    }

    int Find(int x)
    {
        int y=0;
        for(int k=(1<<19);k>=1;k/=2)
            if(y+k<n&&aib[y+k]<x)
                x=x-aib[y+k],y+=k;
        return y+1;
    }

    void Erase(int x)
    {
        int y=Find(x);
        for(int i=y;i<=n;i+=(i&-i))
            --aib[i];
    }
};