Provided by standard library.
FIND searches for a partial string within a string.
The input variable STR1 and STR2 are type STRING, the return value of the function is type STRING.
FIND(STR1, STR2) means: Find the position of the first character where STR2 appears in STR1 for the first time. If STR2 is not found in STR1, then OUT:=0.