import sys
from collections import defaultdict

def main():
    n, m, K = map(int, sys.stdin.readline().split())
    B = list(map(int, sys.stdin.readline().split()))
    R = list(map(int, sys.stdin.readline().split()))
    t = min(n, m)
    
    b_dict = defaultdict(list)
    for b in B:
        rem = b % K
        b_dict[rem].append(b)
    
    r_dict = defaultdict(list)
    for r in R:
        rem = r % K
        r_dict[rem].append(r)
    
    pair_costs = []
    
    for rem in b_dict:
        if rem not in r_dict:
            continue
        B_list = sorted(b_dict[rem], reverse=True)
        R_list = sorted(r_dict[rem], reverse=True)
        i = j = 0
        while i < len(B_list) and j < len(R_list):
            b_val = B_list[i]
            r_val = R_list[j]
            x = max(b_val, r_val)
            diff = x - min(b_val, r_val)
            cost = diff // K
            pair_costs.append(cost)
            i += 1
            j += 1
    
    if len(pair_costs) < t:
        print(-1)
    else:
        pair_costs.sort()
        total = sum(pair_costs[:t])
        print(total)

if __name__ == "__main__":
    main()