31-18 = 13
13 + 30 = 43
43 + 31 = 74
31 - 15 = 16
74 + 16 = 90
дней
(31 -18) + 30 +31 + (31 - 15) = 90
31-18 = 13
13 + 30 = 43
43 + 31 = 74
31 - 15 = 16
74 + 16 = 90
дней
(31 -18) + 30 +31 + (31 - 15) = 90
дней