foo.c: In function 'main':
foo.c:9:14: warning: format '%f' expects argument of type 'float *', but argument 3 has type 'double' [-Wformat=]
    scanf("%d%f",&n,r);
             ~^
foo.c:9:4: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d%f",&n,r);
    ^~~~~~~~~~~~~~~~~~
foo.c:10:4: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%f%f",&x1,&y1);
    ^~~~~~~~~~~~~~~~~~~~~
foo.c:15:8: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
        scanf("%f%f",&x1,&y1);
        ^~~~~~~~~~~~~~~~~~~~~
foo.c:9:4: warning: 'r' is used uninitialized in this function [-Wuninitialized]
    scanf("%d%f",&n,r);
    ^~~~~~~~~~~~~~~~~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。