/in/foo.c:1:1: error: unknown type name 'def'
 def isyeap (year):
 ^~~
/in/foo.c: In function 'isyeap':
/in/foo.c:1:18: error: expected declaration specifiers before ':' token
 def isyeap (year):
                  ^
/in/foo.c:1:5: warning: type of 'year' defaults to 'int' [-Wimplicit-int]
 def isyeap (year):
     ^~~~~~
/in/foo.c:11:1: warning: control reaches end of non-void function [-Wreturn-type]
 print(sum(months[0:n[1]-1]) + n[2])
 ^~~~~