foo.cc: In function 'int main()':
foo.cc:6:16: error: unable to find numeric literal operator 'operator""\U0000ff1b'
    6 |         return 0；
      |                ^~~
foo.cc:6:16: note: use '-fext-numeric-literals' to enable more built-in suffixes
foo.cc:6:19: error: expected ';' before '}' token
    6 |         return 0；
      |                   ^
      |                   ;
    7 | }
      | ~                  

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