#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.pop_back();
    v[1] = 40;
    cout << v.size() << " " << v.front() << " " << v.back() << endl;
    return 0;
}