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 <bits/stdc++.h> //C++の機能を「全て」読み込むための命令
#define rep(i,n) for(int i=0; i<(n); ++i)
#define cout(x) cout<<(x)<<endl
#define all(v) v.begin(), v.end()
using namespace std;
//型エイリアス
using vi = vector<int>;
using ll = long long;
using P = pair<int,int>;
using Mat = vector<vector<int>>;
const ll inf = 1e18;
const int N = 2e5+10;


int main(){
    ll a, b;
    ll x;
    cin >> a >> b >> x;

    ll ans = b/x - a/x;
    if(a%x==0 || b%x==0) ++ans;
    if(a==0 && b==0) ans=0;
    printf("%lld\n",ans);

    return 0;
}