foo.cc: In function 'int hwlength(int)':
foo.cc:19:9: warning: variable 'a' set but not used [-Wunused-but-set-variable]
     int a[10],i=0;  
         ^
foo.cc: In function 'int main()':
foo.cc:45:15: warning: unused variable 'j' [-Wunused-variable]
     int a,b,i,j;  
               ^
foo.cc:46:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d",&a,&b);  
     ~~~~~^~~~~~~~~~~~~~

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