foo.cc: In function 'int main()':
foo.cc:12:9: warning: unused variable 'a' [-Wunused-variable]
     int a,b,c;
         ^
foo.cc:12:11: warning: unused variable 'b' [-Wunused-variable]
     int a,b,c;
           ^
foo.cc:12:13: warning: unused variable 'c' [-Wunused-variable]
     int a,b,c;
             ^
foo.cc:11:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&n);
     ~~~~~^~~~~~~~~

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