function activationKey(arr = []) {
    let key = arr[0];

    for (let i = 1; i < arr.length; i++) {
        const tokens = arr[i].split('>>>');
        const command = tokens[0];

        if (command === 'Generate') {
            break;

        } else if (command === 'Contains') {
            const substring = tokens[1];

            if (key.includes(substring)) {
                console.log(`${key} contains ${substring}`);
            } else {
                console.log('Substring not found!');
            }
        } else if (command === 'Flip'){
            const typeOfCommand = tokens[1];
            const startIndex = Number(tokens[2]);
            const endIndex = Number(tokens[3]);
            let changedKey = key.substring(startIndex, endIndex);

            if (typeOfCommand === 'Lower') {
                changedKey = changedKey.toLowerCase();
                key = key.substring(0, startIndex) + changedKey + key.substring(endIndex);
            } else if (typeOfCommand === 'Upper') {
                changedKey = changedKey.toUpperCase();
                key = key.substring(0, startIndex) + changedKey + key.substring(endIndex);
            }
            console.log(key);
        } else if (command === 'Slice') {
            const startIndex = Number(tokens[1]);
            const endIndex = Number(tokens[2]);

            key = key.substring(0, startIndex) + key.substring(endIndex);

            console.log(key);
        }
    }

    console.log(`Your activation key is: ${key}`);
}