Formula tool- remove last four (4) characters from a string

[Elena_B1]

Hello.

I have a string 500147666122221. I need to create a new column and remove last four digits.

Appreciate your help.

[dYoast · Accepted solution]

Left([YourString], Length[YourString])-4)

[Elena_B1]

I've got the error 

[Elena_B1]

I was able to correct it Left([Reference],Length([Reference])-4)

[Elena_B1]

Thank you for the help