NUMBER789 C++

#include<bits/stdc++.h>
using namespace std;
int n,k,j,res = 0,p[5000005];

void sang()
{
    for(int i = 1; i<=n; i++) p[i] = i;
    for(int i = 2; i<=n/2+1; i++)
    {
        if (p[i] == i)
        {
            j=i*2;
            while(j<=n)
            {
                    p[j]=i;
                    j=j+i;
            }
       

        }
    }
}

void giai()
{
    res=0;
    for(int i=2;i<=n;i++)
    {
        if (p[i] <= k)
        {
            //cout<<i<<" "<<p[i]<<endl;
            res++;
        }
    }
    cout << res;
}
int main()
{
    freopen("NUMBER789.inp","r",stdin);
    freopen("NUMBER789.out","w",stdout);
    cin>>n>> k;
    sang();
    giai();
    return 0;
}