#include <iostream>
#include <vector>
using namespace std;
int main() {
    vector<int> v;
    v.push_back(10);
    v.push_back(20);
    v.push_back(30);
    v.push_back(40);
    v.erase(v.begin() + 2);
    v.push_back(50);
    cout << v.at(3) << endl;
    return 0;
}