Problem:
Score : 200 points

Problem Statement

You are given nonnegative integers a and b (a ≤ b), and a positive integer x.
Among the integers between a and b, inclusive, how many are divisible by x?

Constraints

0 ≤ a ≤ b ≤ 10^{18}

1 ≤ x ≤ 10^{18}

Input

The input is given from Standard Input in the following format:

a b x

Output

Print the number of the integers between a and b, inclusive, that are divisible by x.

Sample Input 1

4 8 2

Sample Output 1

3

There are three integers between 4 and 8, inclusive, that are divisible by 2: 4, 6 and 8.

Sample Input 2

0 5 1

Sample Output 2

6

There are six integers between 0 and 5, inclusive, that are divisible by 1: 0, 1, 2, 3, 4 and 5.

Sample Input 3

9 9 2

Sample Output 3

0

There are no integer between 9 and 9, inclusive, that is divisible by 2.

Sample Input 4

1 1000000000000000000 3

Sample Output 4

333333333333333333

Watch out for integer overflows.

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <fstream>
#include <string>
#include <algorithm>
#include <cstdlib>
#include <vector>
#include <stack>
#include <queue>
#include <complex>
#include <set>
#include <list>
#include <iomanip>
#include <map>
#include <memory.h>



using namespace std;
static const double EPS = 1e-9;
typedef long long ll;
typedef unsigned long long ull;
#define FOR(i,n) for(int i=0;i<(int)n;++i)
#define FORNUM(p, x) for (int num = p; num < (int)(x); ++num)
#define FORI(p, x) for (int i = p; i < (int)(x); ++i)
#define FORJ(p, x) for (int j = p; j < (int)(x); ++j)
#define FORK(p, x) for (int k = p; k < (int)(x); ++k)
#define FORL(p, x) for (int l = p; l < (int)(x); ++l)

typedef pair<int,int>P;
#define INF 1000000000
 
struct edge { 
	int from, to,cap,rev; 
	edge (int from, int to, int cap, int rev){
		this->from=from; this->to=to; this->cap=cap; this->rev=rev;
	}
};
 
int V,E;
typedef vector<edge> edges;
vector<edges> G;



int main(){
	ll a, b, x;
	cin >> a >> b >> x;
	ll c, d;
	c = (a +x-1)/ x;
	d = b  / x;
	cout << d - c + 1 << endl;

	return 0;
}