foo.c: In function 'main':
foo.c:10:17: error: expected ':' or '...' before 'd'
   10 |                 d=a+c;
      |                 ^
foo.c:12:17: error: expected ':' or '...' before 'd'
   12 |                 d=a-c;
      |                 ^
foo.c:10:20: warning: statement will never be executed [-Wswitch-unreachable]
   10 |                 d=a+c;
      |                   ~^~

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