/in/foo.cc: In function 'int main()':
/in/foo.cc:23:7: error: 'i' was not declared in this scope
   for(i=1;i<n;i++)
       ^
/in/foo.cc: In function 'int dfs(int, int, int, int)':
/in/foo.cc:10:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^