foo.c: In function 'main':
foo.c:12:5: error: 'm' undeclared (first use in this function)
   12 |     m=a*b;
      |     ^
foo.c:12:5: note: each undeclared identifier is reported only once for each function it appears in
foo.c: At top level:
foo.c:25:1: error: expected identifier or '(' before '}' token
   25 | }
      | ^

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