codeforces 749

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n,i,j,c=0,z,y=0;
    cin>>n;
    if(n%2!=0)
    {
        z=n-3;
        y=(z/2);
        c=y+1;
    }
    else
    {
        y=n/2;
        c=y;
    }

    cout<<c<<endl;

    for(i=1; i<=y; i++)
    {
        cout<<"2"<<' ';
    }
    if(n%2!=0)
        cout<<"3";


    return 0;
}