I'm trying to multiply a numericUpDown input.Here is my code so far:

double pi = Math.PI;
decimal number1 = numericUpDown1.Value;
int RadiusToCircumference = number1 * 2 * pi;
MessageBox.Show("The circumference is" + RadiusToCircumference);

Dont think im stupid that i didnt figure this out yet. just started programming yesterday.