using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;

namespace Green
{
    using static Ex;
    public class Solve
    {
        public static void Main(string[] args)
        {
            new abc048_b();
        }
    }
    public class abc048_b
    {
        long a, b, x;
        public abc048_b()
        {
            (a, b, x) = ReadLongArray().ToTpl3();
            if (a == 0)
                (b / x + 1).Cw();
            else
                (b / x - (a - 1) / x).Cw();
        }
    }
    public class sumitb2019_d
    {
        public sumitb2019_d()
        {
            var n = ReadInt;
            var s = Read.Select(v => v - '0').ToArray();


            var num = s[0];
            var set = new HashSet<(int, int, int)>();
            set.Add((num, -1, -1));

            for (int i = 1; i < n; i++)
            {
                num = s[i];

                var next = new HashSet<(int, int, int)>();
                next.Add((num, -1, -1));

                foreach (var v in set)
                {
                    if (v.Item3 != -1)
                    {
                        next.Add(v);
                        continue;
                    }

                    if (v.Item2 == -1)
                        next.Add((v.Item1, num, -1));
                    else
                        next.Add((v.Item1, v.Item2, num));
                }
                set = next;

                for (int j = 0; j < 10; j++)
                {
                    for (int k = 0; k < 10; k++)
                    {

                    }
                }
            }
        }
    }
    public class abc148_e
    {
        long res = 0;
        public abc148_e()
        {
            var n = ReadLong;
            f(n);
            res.Cw();
        }

        long f(long n)
        {
            if (n < 2)
            {
                return 1;
            }

            int c = 0;
            var tmp = f(n - 2);
            if (tmp == 0)
            {
                res = 1;
                return 0;
            }

            var s = tmp.ToString();
            for (int i = s.Length - 1; i >= 0; i--)
            {
                if (s[i] != '0') break;

                c++;
            }

            if (c == 0) return n * tmp;

            res += c;
            return n * tmp / (10 * c);
        }
    }
    public class abc_
    {
        public abc_()
        {
        }
    }

    public static class Ex
    {
        public static void Cw(this object s) { Console.WriteLine(s); }



        public static bool Mins<T>(ref T a, T b) where T : IComparable<T> { if (a.CompareTo(b) > 0) { a = b; return true; } return false; }
        public static bool Maxs<T>(ref T a, T b) where T : IComparable<T> { if (a.CompareTo(b) < 0) { a = b; return true; } return false; }
        public static void Swap<T>(ref T a, ref T b) { var t = b; b = a; a = t; }
        public static void Swap<T>(List<T> list, int i, int j) { T tmp = list[j]; list[j] = list[i]; list[i] = tmp; }

        public static long Lcm(int x, int y) { return x / Gcd(x, y) * y; }
        public static long Gcd(long m, long n) { if (n == 0) return m; return Gcd(n, m % n); }
        public static List<string> FastSort(this List<string> s) { s.Sort(StringComparer.Ordinal); return s.ToList(); }
        public static void yesno(this bool b) { (b ? "yes" : "no").Cw(); }
        public static void YesNo(this bool b) { (b ? "Yes" : "No").Cw(); }
        public static void YESNO(this bool b) { (b ? "YES" : "NO").Cw(); }

        public static string Read { get { return Console.ReadLine().Trim(); } }
        public static int ReadInt { get { return int.Parse(Read); } }
        public static long ReadLong { get { return long.Parse(Read); } }
        public static double ReadDouble { get { return double.Parse(Read); } }
        public static string[] ReadArray() { return Read.Split(' '); }
        public static int[] ReadIntArray() { return Read.Split(' ').Select(int.Parse).ToArray(); }
        public static long[] ReadLongArray() { return Read.Split(' ').Select(long.Parse).ToArray(); }
        public static string[] ReadArray(long N) { var v = new string[N]; for (long i = 0; i < N; ++i) v[i] = Read; return v; }
        public static int[] ReadIntArray(long N) { var v = new int[N]; for (long i = 0; i < N; ++i) v[i] = ReadInt; return v; }
        public static long[] ReadLongArray(long N) { var v = new long[N]; for (long i = 0; i < N; ++i) v[i] = ReadLong; return v; }

        public static (T, T) ToTpl2<T>(this T[] v) { return (v[0], v[1]); }
        public static (T, T, T) ToTpl3<T>(this T[] v) { return (v[0], v[1], v[2]); }
        public static (T, T, T, T) ToTpl4<T>(this T[] v) { return (v[0], v[1], v[2], v[3]); }
        public static (T, T, T, T, T) ToTpl5<T>(this T[] v) { return (v[0], v[1], v[2], v[3], v[4]); }


        public static int LowerBound<T>(T[] a, T v)
        {
            return LowerBound(a, v, Comparer<T>.Default);
        }

        public static int LowerBound<T>(T[] a, T v, Comparer<T> cmp)
        {
            var l = 0;
            var r = a.Length - 1;
            while (l <= r)
            {
                var mid = l + (r - l) / 2;
                var res = cmp.Compare(a[mid], v);
                if (res == -1) l = mid + 1;
                else r = mid - 1;
            }
            return l;
        }

        /// <summary>
        /// lower_boundは、探索したいkey以上のイテレータを返す
        /// upper_boundは、探索したいkeyより大きいイテレータを返す
        public static int UpperBound<T>(List<T> a, T v)
        {
            return UpperBound(a, v, Comparer<T>.Default);
        }

        public static int UpperBound<T>(List<T> a, T v, Comparer<T> cmp)
        {
            var l = 0;
            var r = a.Count - 1;
            while (l <= r)
            {
                var mid = l + (r - l) / 2;
                var res = cmp.Compare(a[mid], v);
                if (res <= 0) l = mid + 1;
                else r = mid - 1;
            }
            return l;
        }
    }
}

Measured memory_bytes: 28264