function processData(input) {
    let currentString = '';
    let operationHistory = [];
    const operations = input.split('\n').slice(1); 
    for (let op of operations) {
        const opArr = op.split(' ');
        const type = parseInt(opArr[0]);
        if (type === 1) { 
            const strToAppend = opArr[1];
            currentString += strToAppend;
            operationHistory.push({ type: 1, value: strToAppend }); 
        } else if (type === 2) { // Delete operation
            const numToDelete = parseInt(opArr[1]);
            const deletedString = currentString.slice(-numToDelete); 
            currentString = currentString.slice(0, -numToDelete); 
            operationHistory.push({ type: 2, value: deletedString }); 
        } else if (type === 3) { // Print operation
            const index = parseInt(opArr[1]) - 1; 
            console.log(currentString[index]);

        } else if (type === 4) { 
            const lastOperation = operationHistory.pop();
            if (lastOperation.type === 1) { // Undo append
                const appendedString = lastOperation.value;
                currentString = currentString.slice(0, -appendedString.length); 
            } else if (lastOperation.type === 2) { // Undo delete
                const deletedString = lastOperation.value;
                currentString += deletedString;
            }
        }
    }
}