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 (Clang 10.0.0) (judge verdict: Accepted)

#include<stdio.h>
#include<stdlib.h>
#include<stdbool.h>
#include<string.h>
#include<math.h>
#include<ctype.h>

typedef long long ll;

ll gcd(ll a, ll b) { if (b == 0) return a; return gcd(b, a % b); }

ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }

ll max(ll a, ll b) { return (a > b) ? a : b; }

ll min(ll a, ll b) { return (a < b) ? a : b; }

ll asc(const void* a, const void* b) { return *(ll*)a - *(ll*)b; }

ll dsc(const void* a, const void* b) { return *(ll*)b - *(ll*)a; }

bool flag;

ll f(ll x,ll y) {
	if (x == -1) return -1;
	else return x / y;
}

int main() {
	ll n,a, b;
	scanf("%lld%lld%lld", &a,&b,&n);
	printf("%lld", f(b,n)-f(a-1,n));
	
	return 0;
}