//
// ABC048B
// URL : https://atcoder.jp/contests/abc048/tasks/abc048_b
// 
using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using System.Text;

namespace AtCoder
{
    class ABC048B
    {
        public static readonly long MOD_CONST = 1000000007;//(long)Math.Pow(10, 9) + 7;


        static void Main(string[] args)
        {
            //出力高速化
            var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
            Console.SetOut(sw);
            Solve();
            Console.Out.Flush();
        }
        public static void Solve()
        {
            long[] inputLongArray = Console.ReadLine().Split(' ').Select(_inputStr => long.Parse(_inputStr)).ToArray();
            var a = inputLongArray[0];
            var b = inputLongArray[1];
            var x = inputLongArray[2];
            Console.WriteLine( f(b, x) - f(a-1, x));//[a,b]区間を考える
        }
        /// <summary>
        /// 0以上n以下の整数で条件に合うものの数を計算する
        /// 今回の場合は、xで割り切れるものの数
        /// </summary>
        /// <param name="n">上限</param>
        /// <param name="x">割る数</param>
        /// <returns>[0,n]の範囲でxで割り切れる数</returns>
        public static long f(long n, long x)
        {
            if(n >= 0)
            {
                return n / x + 1;
            }
            return 0;
        }

        //---------------------------------------------------------------------------------

        /// <summary>
        /// 初項a, 公差d, 項数nの数列の和
        /// </summary>
        /// <param name="n">求めたいところ</param>
        /// <returns>初項からxまで足した値</returns>
        static long SumSeries(long a, long d, long n)
        {
            return (2 * a + (n-1) * d) * n / 2;
        }
        /// <summary>
        /// 累積和の配列を計算する
        /// Sum[ a[0], a[i] )がs[i+1]に入っている
        /// s[0]  : 0                //一切和を取らない場合
        /// s[1]  : ls[0]            //a[0]   + s[0] = a[0]
        /// s[2]  : ls[1] + s[1]     //a[1]   + a[0]
        /// ...
        /// s[N]  : ls[N-1] + s[N-1] //a[N-1] + ... + a[0]
        /// s[N+1]: ls[N] + s[N]     //a[N]   + ... + a[0]
        /// 
        /// 例: [1, 7)の和(a[1] + ... + a[6])
        /// s[1] = a[0] //[0, 1)
        /// s[7] = a[0] + a[1] + ... + a[6] //[0, 7)
        /// よってs[7] - s[1]);
        /// </summary>
        /// <param name="ls">計算したい配列</param>
        /// <returns>累積和配列</returns>
        static List<long> AggregateSumList(List<long> a)
        {
            var s = new List<long>(a.Count+1);
            if(a.Count == 0)
            {
                return s;
            }
            s.Add(0);//s[0] = 0
            for(int i = 0; i < a.Count; ++i)
            {
                s.Add(a[i] + s[i]);
            }
            return s;
        }


        /// <summary>
        /// 与えられた数が素数かどうかを計算する
        /// </summary>
        /// <param name="num">対象数</param>
        /// <returns>true:素数, false:素数ではない(合成数)</returns>
        public static bool isPrime(int num)
        {
            if (num < 2) return false;
            else if (num == 2) return true;
            else if (num % 2 == 0) return false;

            double sqrtNum = Math.Sqrt(num);
            for (int i = 3; i <= sqrtNum; i += 2)
            {
                if (num % i == 0)
                {
                    return false;
                }
            }
            return true;
        }

        /// <summary>
        /// 順列mPnを計算する
        /// </summary>
        /// <param name="m"></param>
        /// <param name="n"></param>
        /// <returns></returns>
        public static long Permutation(long m, long n)
        {
            long ret = 1;
            for(var i = 0; i < n; ++i)
            {
                ret *= m - i;
            }
            return ret;
        }
        /// <summary>
        /// 組み合わせmCnを計算する
        /// </summary>
        /// <param name="m"></param>
        /// <param name="n"></param>
        /// <returns></returns>
        public static long Combination(long m, long n)
        {
            if (m == n || n == 0)
            {
                return 1;
            }
            long ans = 1;
            for (var i = 1; i <= n; ++i)
            {
                ans = ans * (m - i + 1) / i;
            }
            return ans;
        }

        static long Gcd(long m, long n)
        {
            if (n == 0) return m;
            return Gcd(n, m % n);
        }

        static long Lcm(long m, long n)
        {
            var gcd = Gcd(m, n);
            //return (m * n) / gcd;
            return m / gcd * n;//桁あふれ対策
        }
    }
}



Measured memory_bytes: 13396