push front of vector c++

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

int main() {
    vector<int> vec;
    vec.insert(vec.begin(), 10);
    vec.insert(vec.begin(), 20);
    vec.insert(vec.begin(), 30);

    for (int i = 0; i < vec.size(); i++) {
        cout << vec[i] << " ";
    }

    return 0;
}