How to pivot a vector of vectors

I am looking for an elegant way to pivot a vector of vector prefarably using STL algorithms or boost Sample data looks like this

vector<vector<int> > vm;
vector<int> v;
v.push_back(1);
v.push_back(2);
vm.push_back(v);
v.clear();
v.push_back(3);
v.push_back(4);
vm.push_back(v);
v.clear();
v.push_back(5);
v.push_back(6);
vm.push_back(v);

1   2
3   4
5   6

I want to get a vector of vectors of ints like this

1   3   5
2   4   6