#include <iostream>
#include <vector>

using namespace std;

int main()
{
    vector< vector<char> > vv = { { 'a', 'b' }, { 'c', 'd' } };
    for (auto& v : vv)
    {
        for (auto& n : v)
            cout << n << " ";
        cout << endl;
    }
    return 0;
}