/in/foo.cc: In function 'void kruskal(int, int)':
/in/foo.cc:47:115: warning: suggest parentheses around comparison in operand of '!=' [-Wparentheses]
                                                                      if (day[j][u][v]-day[i-1][u][v]!=0 || find(u)==find(v)!=0)                                                                                                                            continue;
                                                                                                            ~~~~~~~^~~~~~~~~