foo.c:2:2: error: invalid preprocessing directive #\U00008bf7\U00008ba1\U00007b97\U00006b63\U000065b9\U00005f62\U00007684\U00009762\U000079ef
    2 | #请计算正方形的面积
      |  ^~~~~~~~~~~~~~~~~~
foo.c:3:1: warning: data definition has no type or storage class
    3 | a=int(input())
      | ^
foo.c:3:1: warning: type defaults to ‘int’ in declaration of ‘a’ [-Wimplicit-int]
foo.c:3:3: error: expected expression before ‘int’
    3 | a=int(input())
      |   ^~~