#include <iostream>
#include <vector>
#include <cstddef>

int main()
{
    using std::cin;
    using std::cout;
    using std::endl;
    using std::size_t;
    
    std::vector<double> miles(4);
    std::vector<double> gallons(4);
    for (size_t i = 0; i <= 4; ++i) // off-by-one error (OBOE)
    {
        cout << "Miles: ";
        cin >> miles.at(i);
        cout << "\nGallons: ";
        cin >> gallons.at(i);
        cout << endl;
    } 
}