Vector of random interger sets

I'm trying to write a little program to create a vector of random integer sets, but the problem is once the first set is created the program keeps storing the same set of numbers in subsequent iterations. Any help to explain or correct this problem would be very much appreciated. Thanks!

#include<iostream>
#include<cstdlib>
#include<ctime>
#include<set>
#include<vector>
using namespace std;
typedef set<int> Set_I;
typedef set<int>::iterator It;
typedef vector<set<int> > vec_Set;


int random();
void print_set(Set_I s);
void print_vec(vec_Set v);

int main()
{   
    srand(time(0));

    Set_I s;
    vec_Set v;
    v.resize(4);
    for(int i=0; i<4;i++)
    {

        //cout << s.size() << " " <<endl;
        while(s.size()<6)
        {
            s.insert(random());

        }

        v[i] = s;
        s.empty();


    }
    //print_set(s);
    print_vec(v);

    cout << endl << s.size() <<endl << v.size();
    system("PAUSE");
}

int random()
{
    int r = 1 + rand()%49;
    return r;
}

void print_set(Set_I s)
{
    for(It it=s.begin(); it!=s.end(); it++)
        {
            cout << *it << " ";
        }
        cout << endl;
}

void print_vec(vec_Set v)
{
        for(int i=0;i<v.size();i++)
        {
            cout << "{ ";
            for(It j = v[i].begin() ; j != v[i].end() ;j++)
            {
                cout << *j << " ";
            }
            cout <<"}";
            cout <<endl;
        }[enter image description here][1]
}