foo.c: In function 'main':
foo.c:5:41: error: 'c\U0000ff0cx' undeclared (first use in this function)
    5 |         printf("%d\n%d\n%d\n%d\n%d",a,b,c，x,y);
      |                                         ^~~~
foo.c:5:41: note: each undeclared identifier is reported only once for each function it appears in
foo.c:3:28: warning: variable 'x' set but not used [-Wunused-but-set-variable]
    3 |         int a=15,b=18,c=21,x,y;
      |                            ^

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