/in/foo.cc: In function 'int main()':
/in/foo.cc:9:7: warning: unused variable 'a' [-Wunused-variable]
   int a,b[Maxlen]={0},lena,lenb,lenc,x,n;
       ^
/in/foo.cc:9:23: warning: unused variable 'lena' [-Wunused-variable]
   int a,b[Maxlen]={0},lena,lenb,lenc,x,n;
                       ^~~~
/in/foo.cc:9:33: warning: variable 'lenc' set but not used [-Wunused-but-set-variable]
   int a,b[Maxlen]={0},lena,lenb,lenc,x,n;
                                 ^~~~