// For C++ libraries.
#include <iostream>

// Library for strings.
#include<string>

using namespace std;

int main() {
    string word="Book";
    string word2="airplane";

    cout << word << endl;
    word[1]='i';
    word[2]=word[3];
    word[3]='e';
    cout << word << endl;

    cout << endl;

    cout << word2.substr(0,3) << endl;

    return 0;

}