Little penguin Polo has an n × m matrix, consisting of integers. Let's index the matrix rows from 1 to n from top to bottom and let's index the columns from 1 to m from left to right. Let's represent the matrix element on the intersection of row i and column j as aij.

In one move the penguin can add or subtract number d from some matrix element. Find the minimum number of moves needed to make all matrix elements equal. If the described plan is impossible to carry out, say so.

Input

The first line contains three integers n, m and d (1 ≤ n, m ≤ 100, 1 ≤ d ≤ 104) — the matrix sizes and the d parameter. Next n lines contain the matrix: the j-th integer in the i-th row is the matrix element aij (1 ≤ aij ≤ 104).

Output

In a single line print a single integer — the minimum number of moves the penguin needs to make all matrix elements equal. If that is impossible, print "-1" (without the quotes).

Examples

Input

2 2 2
2 4
6 8


Output

4


Input

1 2 7
6 7


Output

-1
#===========Template===============
from io import BytesIO, IOBase
from math import sqrt
import sys,os
from os import path
inpl=lambda:list(map(int,input().split()))
inpm=lambda:map(int,input().split())
inpi=lambda:int(input())
inp=lambda:input()
rev,ra,l=reversed,range,len

P=print
BUFSIZE = 8192
class FastIO(IOBase):
    newlines = 0

    def __init__(self, file):
        self._fd = file.fileno()
        self.buffer = BytesIO()
        self.writable = "x" in file.mode or "r" not in file.mode
        self.write = self.buffer.write if self.writable else None

    def read(self):
        while True:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            if not b:
                break
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines = 0
        return self.buffer.read()

    def readline(self):
        while self.newlines == 0:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            self.newlines = b.count(b"\n") + (not b)
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines -= 1
        return self.buffer.readline()

    def flush(self):
        if self.writable:
            os.write(self._fd, self.buffer.getvalue())
            self.buffer.truncate(0), self.buffer.seek(0)

class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        self.write = lambda s: self.buffer.write(s.encode("ascii"))
        self.read = lambda: self.buffer.read().decode("ascii")
        self.readline = lambda: self.buffer.readline().decode("ascii")


sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
def input(): return sys.stdin.readline().rstrip("\r\n")

def B(n):
    return bin(n).replace("0b","")

def factors(n):
    arr=[]
    for i in ra(2,int(sqrt(n))+1):
        if n%i==0:
            arr.append(i)
            if i*i!=n:
                arr.append(int(n/i))
    return arr  

def dfs(arr,n):
    pairs=[[i+1] for i in ra(n)]
    vis=[0]*(n+1)
    for i in ra(l(arr)):
        pairs[arr[i][0]-1].append(arr[i][1])
    pairs[arr[i][1]-1].append(arr[i][0])
    
    comp=[]
    for i in ra(n):
        stack=[pairs[i]]
        temp=[]
        if vis[stack[-1][0]]==0: 
            while len(stack)>0:
                if vis[stack[-1][0]]==0:
                    temp.append(stack[-1][0])
                    vis[stack[-1][0]]=1
                    s=stack.pop()
                    for j in s[1:]:
                        if vis[j]==0:
                            stack.append(pairs[j-1])
                else:
                    stack.pop()
            comp.append(temp)
    return comp
    
  
#=========I/p O/p ========================================#
from bisect import bisect_left as bl 
from bisect import bisect_right as br
import sys,operator,math,operator
from collections import Counter 
if(path.exists('input.txt')):
    sys.stdin = open("input.txt","r")
    sys.stdout = open("output.txt","w")
import random
#==============To chaliye shuru krte he ====================#
n,m,d=inpm()
li=[]
for i in ra(n):li.extend(inpl())

li.sort();tr=True
for i in ra(1,l(li)):
    if (li[i]-li[i-1])%d!=0:
        tr=False
        break
if tr:
    med=li[l(li)>>1]
    ans=0
    for i in ra(l(li)):
      
        ans+=(abs(med-li[i])/d)
    P(int(ans))
else:P(-1)