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++ (GCC 9.2.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
using namespace std;
long long int mod = 1000000007;
typedef long long int lli;
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef vector<lli> vlli;
typedef vector<bool> vb;
long long int max(long long int a,long long int b){
  if(a>b)
    return a;
  else
    return b;
}
long long int min(long long int a,long long int b){
  if(a<b)
    return a;
  else
    return b;
}
long long int binpow(long long a, long long b, long long m) {
  a %= m;
  long long res = 1;
  while (b > 0) {
    if (b & 1)
      res = res * a % m;
      a = a * a % m;
      b >>= 1;
    }
  return res;
}
long long binpow(long long a, long long b) {
    if (b == 0)
        return 1;
    long long res = binpow(a, b / 2);
    if (b % 2)
        return res * res * a;
    else
        return res * res;
}
 
//############################ENDOFTEMPLATE############################

void solve(){
  lli a,b,x;
  cin>>a>>b>>x;

  lli lo = (x+a-1)/x;
  lli hi = (b/x);

  cout<<hi-lo+1; 
}
 
 
 
 
int main(){
  ios::sync_with_stdio(0);
  cin.tie(0);
  //freopen("moobuzz.in","r",stdin);
  //freopen("moobuzz.out","w",stdout);
  int t = 1;
  //cin>>t;
  while(t--){
    solve();
  }
}