foo.c: In function 'main':
foo.c:5:9: error: 'n' undeclared (first use in this function)
    5 |         n=0;
      |         ^
foo.c:5:9: note: each undeclared identifier is reported only once for each function it appears in
foo.c:7:21: error: 'a' undeclared (first use in this function)
    7 |         scanf("%d",&a);
      |                     ^
foo.c:8:14: warning: unused variable 'arr' [-Wunused-variable]
    8 |         char arr[a];
      |              ^~~
foo.c:4:13: warning: unused variable 'n\U0000ff0ca' [-Wunused-variable]
    4 |         int n，a;
      |             ^~~~

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