/in/foo.cc: In function 'void dfs(int)':
/in/foo.cc:101:5: warning: 'k' may be used uninitialized in this function [-Wmaybe-uninitialized]
     if(j!=k)return;
     ^~
/in/foo.cc:101:5: warning: 'k' may be used uninitialized in this function [-Wmaybe-uninitialized]
     if(j!=k)return;
     ^~
/in/foo.cc: In function 'int main()':
/in/foo.cc:101:5: warning: 'k' may be used uninitialized in this function [-Wmaybe-uninitialized]
     if(j!=k)return;
     ^~
/in/foo.cc:31:7: note: 'k' was declared here
   int k;
       ^