foo.cc: In function 'int main()':
foo.cc:10:30: warning: unused variable 'h' [-Wunused-variable]
     int  head1,back2,i,n,k,j,h;
                              ^
foo.cc:11:10: warning: unused variable 'head' [-Wunused-variable]
     char head,back,a[50];
          ^~~~
foo.cc:12:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d %d",&head1,&back2,&n);
     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:17:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%c",&a[i]);
         ~~~~~^~~~~~~~~~~~

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