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 5.4.1) (judge verdict: Wrong Answer)

#include<stdio.h>
  long long int N,x,ans=0,b;
  long long int a[100010]={};
int p(){
  int i;
  for(i=1;i<=N;i++){
    if(a[i]+a[i+1]>x){
      return 0;
    }
  }
    return 1;
}
int q(){
  int i;
  for(i=1;i<=N-1;i++){
    if(a[i]+a[i+1]>x){
      if(a[i]>a[i+1]){a[i]--;ans++;}
      else if(a[i-1]+a[i]>x){a[i]--;ans++;}
      else{a[i+1]--;ans++;}
    }
  }
}
 
int main(){
  int i;
  scanf("%lld %lld",&N,&x);
  for (i=1;i<=N;i++){
    scanf("%lld",&a[i]);
  }
  while(p()==0){
    q();
  }
  printf("%lld\n",ans);
}