import sys

for line in sys.stdin:
    a = line.split("\n")[0].split(" ")
    l = int(a[0])
    r = int(a[1])
    x = int(a[2])
    res = -1
    for i in range(l,r+1,1):
        if i % x == 0:
            res = i
            break
    print(res)

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