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: Wrong Answer)

#include <iostream>
#include <algorithm>
#include <limits>
#include <vector>
#include <map>
#include <cmath>
#include <limits>
#include <iomanip>
#include <queue>
#include <string.h>
#include <bitset>
#define ll long long int
#define ld long double
#define rep(i,n) for(int i = 0;i < n;i++)
#define rep1(i,n) for(int i = 1;i < n;i++)
#define co(x) cout << x << endl
#define cosp(x) cout << x << " "
#define all(x) x.begin(),x.end()
#define allr(x) x.begin(),x.end(),greater<int>()
#define P pair<ll,ll>
#define pb push_back
#define mp make_pair
#define MOD 1000000007
#define INF 1ll << 60
#define PI 3.14159265359

using namespace std;

int main(){
	ll a,b,x;
	cin >> a >> b >> x;
	ll ans;
	ans = b/x - (a-1)/x;
	cout << ans << endl;
    return 0;
}