foo.c: In function 'main':
foo.c:5:15: error: expected '=', ',', ';', 'asm' or '__attribute__' before '<' token
    5 |  for(int n=2,n<a,n++)
      |               ^
foo.c:11:1: error: expected expression before 'if'
   11 | if n==a-1
      | ^~
foo.c:13:2: error: expected expression before 'else'
   13 |  else
      |  ^~~~
foo.c:18:1: error: expected expression before '}' token
   18 | }
      | ^
foo.c:5:10: warning: unused variable 'n' [-Wunused-variable]
    5 |  for(int n=2,n<a,n++)
      |          ^

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