foo.cc: In function 'int main()':
foo.cc:4:7: warning: unused variable 'a' [-Wunused-variable]
 char *a;
       ^
foo.cc:5:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d%d",&n,&x);
 ~~~~~^~~~~~~~~~~~~~

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