#include <iostream>
#include <vector>

using namespace std;

int main() {


    int a{-999};
    vector<int>data{1,3,5,7,9};
    int b{999};
    cout << a << b << endl << endl;

    cout << "Data[data.size()] is " << endl;
    cout << endl;

    // won't throw an exception, just bad results.
    cout << data[data.size()] << endl;
    cout << endl;
    cout << "Data.at(data.size()) is " << endl;
    cout << endl;

    // this will trow an exception, no bad data here.
    cout << "We will not see this "  << data.at(data.size()) << endl;
    cout << endl;


    return 0;
}