/in/foo.cc: In function 'int main()':
/in/foo.cc:6:6: warning: unused variable 'a' [-Wunused-variable]
  int a[10000]={0},b[10000]={0},lena=0,lenb=0,lenc=0;
      ^
/in/foo.cc:6:19: warning: unused variable 'b' [-Wunused-variable]
  int a[10000]={0},b[10000]={0},lena=0,lenb=0,lenc=0;
                   ^