#include <iostream> 
#include <vector> 

int main(){

    std::vector<std::vector<int>> vec = {{0,1},{2,3}};
    
    vec.push_back({4,5});
    vec.push_back({5,6});

    for (auto &vec2 : vec){
        for (auto value : vec2){
            std::cout << value << std::endl; 
        }
    }

    return 0;
}