/in/foo.cc: In function 'void dfs1(int, int)':
/in/foo.cc:19:7: warning: unused variable 'v2' [-Wunused-variable]
   int v2;
       ^
/in/foo.cc: In function 'void dfs2(int, int)':
/in/foo.cc:32:7: warning: unused variable 'v2' [-Wunused-variable]
   int v2;
       ^