foo.cc: In function 'int main()':
foo.cc:21:28: error: unable to find numeric literal operator 'operator""c1'
   21 |                         c1=2c1-a1;
      |                            ^~~
foo.cc:21:28: note: use '-fext-numeric-literals' to enable more built-in suffixes
foo.cc:24:29: error: redeclaration of 'int tmp'
   24 |                         int tmp=b2;
      |                             ^~~
foo.cc:19:29: note: 'int tmp' previously declared here
   19 |                         int tmp=b1;
      |                             ^~~

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