#include <iostream>

#include <deque>

using namespace std;

​

int main() {

  deque<string> cars = {"Volvo", "BMW", "Ford", "Mazda"};

​

  // Change the value of the first element

  cars.at(0) = "Opel";

​

  cout << cars.at(0); 

  return 0;

}

​