proc getchar_unlocked():char {. importc:"getchar_unlocked",header: "" .} proc scan(): int = while true: var k = getchar_unlocked() if k < '0' or k > '9': break else: result = 10 * result + k.ord - '0'.ord proc scanN(): int = var pre : char while true: var k = getchar_unlocked() if k < '0' : break pre = k return pre.ord - '0'.ord let n = scanN() if n in [0,1,5,6]: if getchar_unlocked() == '0': echo 1 else: echo n quit 0 var c = getchar_unlocked() if c == '0': quit "1", 0 if n in [4,9]: while true: let k = getchar_unlocked() if k < '0' : let last = (c.ord - '0'.ord) mod 2 if n == 4: echo [6,4][last] elif n == 9: echo [1,9][last] quit 0 c = k else: var d = '0' while true: let k = getchar_unlocked() if k < '0' : let last = ((d.ord - '0'.ord) * 10 + (c.ord - '0'.ord)) mod 4 if n == 2: echo [6,2,4,8][last] elif n == 3: echo [1,3,9,7][last] elif n == 7: echo [1,7,9,3][last] elif n == 8: echo [6,8,4,2][last] quit 0 d = c c = k