foo.c:1:1: warning: data definition has no type or storage class
    1 | r=input("input a number please")
      | ^
foo.c:1:1: warning: type defaults to 'int' in declaration of 'r' [-Wimplicit-int]
foo.c:1:3: warning: implicit declaration of function 'input' [-Wimplicit-function-declaration]
    1 | r=input("input a number please")
      |   ^~~~~
foo.c:1:3: error: initializer element is not constant
foo.c:2:9: error: expected ',' or ';' before 'v'
    2 |         v=4/3*PI*r*r*r
      |         ^

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