C++ alias template

#include <vector>
#include <iostream>
using namespace std;

template<class T> using vec1D = vector<T>;
template<class T> using vec2D = vector<vec1D<T>>;
template<class T> using vec3D = vector<vec2D<T>>;

int main(){

    vec3D<int> v1 = {{{0},{1},{2}},{{3},{4},{5}},{{6},{7},{8}}};

    for (int i=0;i<3;i++) {
        for (int j=0;j<3;j++) {
            for (int k=0;k<3;k++) cout << v1[i][j][k];
            cout <<" ";
        }
        cout << endl;
    }

    return 0;
}