n[0]-n[1]|n[1]-n[2]
n[0]*6-n[1]*5-n[2]
n[2-i]+=n[2-i]-7?1:-6;
n[2-i]=n[2-i]%7+1;

n[0]*6-n[1]*5-n[2]はちゃんと動くか分からん