foo.c:1:1: error: unknown type name 'def'
    1 | def calculate_bottles(n):
      | ^~~
foo.c: In function 'calculate_bottles':
foo.c:1:25: error: expected declaration specifiers before ':' token
    1 | def calculate_bottles(n):
      |                         ^
foo.c:1:5: warning: type of 'n' defaults to 'int' [-Wimplicit-int]
    1 | def calculate_bottles(n):
      |     ^~~~~~~~~~~~~~~~~
foo.c:21: warning: control reaches end of non-void function [-Wreturn-type]

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