ws1s; ex1 x1: ex1 x2: ex1 x3: ex1 x4: ex1 x5: ex1 x6: ex1 x7: ex1 x8: ex1 x9: ex1 x10: ex1 x11: ex1 x12: ex1 x13: ex1 x14: ex1 x15: ex1 x16: ex1 x17: ex1 x18: ex1 x19: x1 < x2 & x2 < x3 & x3 < x4 & x4 < x5 & x5 < x6 & x6 < x7 & x7 < x8 & x8 < x9 & x9 < x10 & x10 < x11 & x11 < x12 & x12 < x13 & x13 < x14 & x14 < x15 & x15 < x16 & x16 < x17 & x17 < x18 & x18 < x19;