from collections import defaultdict, deque
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()
b = li()
r = li()

db = defaultdict(list)
dr = defaultdict(list)
for bb in b:
    db[bb % k].append(bb)
for rr in r:
    dr[rr % k].append(rr)

cost = 0
cnt = 0


def solve(x, y):
    n = len(x)
    m = len(y)
    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]
            if nxt[j + 1] > abs(x[i] - y[j]) + mn:
                nxt[j + 1] = abs(x[i] - y[j]) + mn
        dp = nxt
    return dp[m]

for ky in db.keys():
    if ky not in dr:
        continue
    x = deque(sorted(db[ky][:]))
    y = deque(sorted(dr[ky][:]))

    if len(x) > len(y):
        x, y = y, x

    cost += solve(x, y)
    cnt += len(x)

if cnt == min(n, m):
    print(cost // k)
else:
    print(-1)