Airtable If-statement outputting NaN

I'm using an If-statement to assign integers to strings from another cell. This seems to be working, but if I reference these columns, I'm getting a NaN value. This is my formula below. I tried adding INT() around the output values, but that seemed to break everything. Am I missing something?

IF(FIND('1',{Functional response}),-4,
IF(FIND('2',{Functional response}),-2,
IF(FIND('3',{Functional response}),0,
IF(FIND('4',{Functional response}),2,
IF(FIND('5',{Functional response}),4,"")))))