02.FromLeftToTheRight

//INPUT
short linesCount = short.Parse(Console.ReadLine());

//CHANGEABLE
int firstNumberDigitsSum = 0;
int secondNumberDigitsSum = 0;

//ACTION
for (int i = 1; i <= linesCount; i++)
{
    string input = Console.ReadLine();
    var result = input.Split(" ");

    long firstNumber = long.Parse(result[0]);
    long secondNumber = long.Parse(result[1]);

    firstNumberDigitsSum = 0;
    secondNumberDigitsSum = 0;

    int firstNumberLength = result[0].Length;
    int secondNumberLength = result[1].Length;

    //Digits Sum
    for (int j = 1; j <= firstNumberLength; j++)
    {
        long lastDigitFirstNum = firstNumber % 10;
        firstNumberDigitsSum += (int)lastDigitFirstNum;
        firstNumber /= 10;
    }

    for (int k = 1; k <= secondNumberLength; k++)
    {
        long lastDigitSecondNum = secondNumber % 10;
        secondNumberDigitsSum += (int)lastDigitSecondNum;
        secondNumber /= 10;
    }

    //Comparing
    if (firstNumberDigitsSum > secondNumberDigitsSum)
    {
        Console.WriteLine(firstNumberDigitsSum);
    }
    else
    {
        Console.WriteLine(secondNumberDigitsSum);
    }
}