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
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.*;
public class Main{
    public static void main(String[] args) {
        FastScanner sc = new FastScanner();
        PrintWriter out = new PrintWriter(System.out);
        int n=sc.nextInt();
        int m=sc.nextInt();
        int d=sc.nextInt();
        int min=Integer.MAX_VALUE;
        int max=Integer.MIN_VALUE;
        int a[][]=new int[n][m];
        boolean flag=true;
        int x=-1;
        for (int i=0;i<n;i++){
            for (int j=0;j<m;j++){
                a[i][j]=sc.nextInt();
                min=Math.min(a[i][j],min);
                max=Math.max(a[i][j],max);
                if (x==-1){
                    x=a[i][j]%d;
                }
                else if (a[i][j]%d!=x){
                    flag=false;
                }
            }
        }
        if (flag==false){
            System.out.println(-1);
        }
        else{
            int ans=Integer.MAX_VALUE;
            for (x=min;x<=max;x+=d){
                int moves=0;
                for (int i=0;i<n;i++){
                    for (int j=0;j<m;j++){
                        moves+=Math.abs(a[i][j]-x)/d;
                    }
                }
                ans=Math.min(ans,moves);
            }
            System.out.println(ans);
        }




        out.flush();
    }
    //-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

    static class Binary implements Comparable<Binary>{
        int num;
        int val;
        Binary(int n,int v){
            num=n;
            val=v;
        }
        public int compareTo(Binary o){
            return val-o.val;
        }
    }
    static void sort(int[] a) {
        ArrayList<Integer> l=new ArrayList<>();
        for (int i:a) l.add(i);
        Collections.sort(l);
        for (int i=0; i<a.length; i++) a[i]=l.get(i);
    }

    static class Pair{
        int i,j;
        Pair(int i,int j){
            this.i=i;
            this.j=j;
        }
    }
    static int mod=(int)1e9+7;
    static long mod(long x){
        return ((x%mod+mod)%mod);
    }
    static long add(long x,long y){
        return mod(mod(x)+mod(y));
    }
    static long mul(long x,long y){
        return mod(mod(x)*mod(y));
    }
    static int[] find(int n,int start,int diff){
        int a[]= new int[n];
        a[0]=start;
        for (int i=1;i<n;i++)a[i]=a[i-1]+diff;
        return a;
    }
    static void swap(int a,int b){
        int c=a;
        a=b;
        b=c;
    }

    static void printArray(int a[]){
        for (int i=0;i<a.length;i++){
            System.out.print(a[i]+" ");
        }
    }
    static boolean sorted(int a[]){
        int n=a.length;
        boolean flag=true;
        for (int i=0;i<n-1;i++){
            if (a[i]>a[i+1])flag=false;
        }
        if (flag)return true;
        else  return false;
    }
    public static int findlog(long n){
        if(n == 0)
            return 0;

        if(n == 1)
            return 0;
        if(n == 2)
            return 1;
        double num = Math.log(n);
        double den = Math.log(2);
        if(den == 0)
            return 0;
        return (int)(num/den);
    }
    public static long gcd(long a,long b){
        if(b%a == 0)
            return a;
        return gcd(b%a,a);
    }
    public static int gcdInt(int a,int b){

        if(b%a == 0)
            return a;

        return gcdInt(b%a,a);

    }

    static void sortReverse(long[] a) {
        ArrayList<Long> l=new ArrayList<>();
        for (long i:a) l.add(i);
//        Collections.sort.(l);
        Collections.sort(l,Collections.reverseOrder());
        for (int i=0; i<a.length; i++) a[i]=l.get(i);
    }

    static class FastScanner {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st=new StringTokenizer("");
        String next() {
            while (!st.hasMoreTokens())
                try {
                    st=new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }
        int[] readArray(int n) {
            int[] a=new int[n];
            for (int i=0; i<n; i++) a[i]=nextInt();
            return a;
        }
        long[] readArrayLong(long n) {
            long[] a=new long[(int)n];
            for (int i=0; i<n; i++) a[i]=nextLong();
            return a;
        }
        long nextLong() {
            return Long.parseLong(next());
        }
    }


}