import sys
l,r,x = map(int,sys.stdin.readline().strip().split())
# print(l)
# print(r)
# print(x)
flag = 0
num = 0
for i in range(l,r+1):
    if i % x == 0:
        flag = 1
        num = i
if flag:
    print(num)
else:
    print('-1')