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 <math.h>

#include <algorithm>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <string>
#include <vector>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); i++)
using ll = long long;
using P = pair<int, int>;

int main() {
  int l, r, d;
  cin >> l >> r >> d;

  int ans = r / d - l / d;

  if (d == 1) {
    ans++;
  } else if (l == d) {
    ans++;
  }
  cout << ans;
  return 0;
}