/in/foo.cc: In function 'int main()':
/in/foo.cc:22:23: warning: 'root' may be used uninitialized in this function [-Wmaybe-uninitialized]
         f[x][0]=cost[x];
                 ~~~~~~^
/in/foo.cc:51:16: note: 'root' was declared here
     ll i,x,k,y,root,j;
                ^~~~