00.Demo

int minNum = int.MaxValue;
int maxNum = int.MinValue;//-2147483648

string input = Console.ReadLine(); //Stop
bool isTrue = false;

while (input != "Stop")
{
    isTrue = true;
    int num = int.Parse(input);

    if (num < minNum)
    {
        minNum = num;
    }
    if (num > maxNum)
    {
        maxNum = num;
    }

    input = Console.ReadLine();
}

if (isTrue)
{
    Console.WriteLine($"minNum: {minNum}");
    Console.WriteLine($"maxNum: {maxNum}");
}