/in/foo.cc: In function 'void find(int)':
/in/foo.cc:16:11: warning: unused variable 'j' [-Wunused-variable]
     int i,j,k,x=f[u].size()-1,v;
           ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:36:11: warning: unused variable 'j' [-Wunused-variable]
     int i,j,k,u,v;
           ^
/in/foo.cc:36:13: warning: unused variable 'k' [-Wunused-variable]
     int i,j,k,u,v;
             ^
/in/foo.cc: In function 'void find(int)':
/in/foo.cc:26:15: warning: 'k' may be used uninitialized in this function [-Wmaybe-uninitialized]
     fo(i,0,x) if(i!=k) cibig=max(cibig,w[f[u][i]]);
               ^~