x1 = x1 x2 = x10 x3 = x11 x4 = x12 x5 = x13 x6 = x14 x7 = x15 x8 = x16 x9 = x17 x10 = x18 x11 = x19 x12 = x2 x13 = x20 x14 = x21 x15 = x22 x16 = x23 x17 = x24 x18 = x25 x19 = x3 x20 = x4 x21 = x5 x22 = x6 x23 = x7 x24 = x8 x25 = x9