Problem:
Score : 100 points

Problem Statement

How many multiples of d are there among the integers between L and R (inclusive)?

Constraints

All values in input are integers.

1 \leq L \leq R \leq 100

1 \leq d \leq 100

Input

Input is given from Standard Input in the following format:

L R d

Output

Print the number of multiples of d among the integers between L and R (inclusive).

Sample Input 1

5 10 2

Sample Output 1

3

Among the integers between 5 and 10, there are three multiples of 2: 6, 8, and 10.

Sample Input 2

6 20 7

Sample Output 2

2

Among the integers between 6 and 20, there are two multiples of 7: 7 and 14.

Sample Input 3

1 100 1

Sample Output 3

100

Solution in C++ (GCC 9.2.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>

using namespace std;

#define int long long
#define rep(i,a,n) for(int i = a; i<n; i++)
#define per(i,a,n) for(int i = n-1; i>=a; i--)

int max(int a,int b){return a>b ? a:b;}
int min(int a,int b){return a<b ? a:b;}


const int INF = 1e9+7;

int n,m,d;

signed main(){
  ios_base::sync_with_stdio(false);
  cin.tie(0);

  cin>>n>>m>>d;

  n += ((d-(n%d))%d);
  m -= (m%d);
  if(m>=n){
    cout<<(m-n)/2 + 1<<"\n";
  }else cout<<"0\n";

}