from collections import defaultdict
import sys

int1 = lambda x: int(x) - 1

# input = lambda: sys.stdin.buffer.readline()
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
i1 = lambda: int1(input())
mi = lambda: map(int, input().split())
mi1 = lambda: map(int1, input().split())
li = lambda: list(mi())
li1 = lambda: list(mi1())
lli = lambda n: [li() for _ in range(n)]

INF = float("inf")
# mod = int(1e9 + 7)
mod = 998244353

N, M, k = mi()
db = defaultdict(list)
dr = defaultdict(list)
for bb in sorted(li()):
    db[bb % k].append(bb)
for rr in sorted(li()):
    dr[rr % k].append(rr)

if N > M:
    db, dr = dr, db


cost = 0
cnt = 0

for ky in db.keys():
    if ky not in dr:
        print(-1)
        exit(0)
    x = db[ky]
    y = dr[ky]

    n = len(x)
    m = len(y)
    if n > m:
        print(-1)
        exit(0)

    dp = [INF] * (m + 1)
    dp[0] = 0
    for i in range(n):
        nxt = [INF] * (m + 1)
        mn = INF
        for j in range(m):
            if mn > dp[j]:
                mn = dp[j]
            d = x[i] - y[j] if x[i] > y[j] else y[j] - x[i]
            nxt[j + 1] = mn + d
        dp = nxt
    cost += min(dp)

print(cost // k)