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)

//失敗するからこそそこから立ち向かって行く強さがあってそんな強さが本当の強さだと私は思うから
// ぜったいあきらめない
#include<bits/stdc++.h>
using namespace std;
 
#if defined(DAIJOBU)
#include "/home/ichigo/debug.hpp"
#define deb(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
#define deb(x...)
#endif
#define FIO {ios::sync_with_stdio(0);cin.tie(nullptr);cout.tie(nullptr);}


int main(){
	FIO
	
	long long a, b, x;cin >> a >> b >> x;
	if(a == 0){
		cout << b / x + 1;
	}
	else{
		long long left = (a - 1) / x;
		long long right = b / x;
		cout << right - left;
	}
	return 0;
}