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: Accepted)

#include <bits/stdc++.h>
//#include <boost/multiprecision/cpp_int.hpp>
using namespace std;
//using namespace boost::multiprecision;
typedef long long int ll;
typedef long double ld;
#define MOD 1000000007
#define ALL(obj) (obj).begin(),(obj).end()
template<class T>inline bool chmax(T& a,T b){if (a<b){a=b;return 1;}return 0;}
template<class T>inline bool chmin(T& a,T b){if (a>b){a=b;return 1;}return 0;}
const long long INF = 1LL << 60;
bool pairCompare(const pair<double,ll>& firstElof, const pair<double,ll>& secondElof){
    return firstElof.first < secondElof.first;
}
bool pairCompareSecond(const pair<double,ll>& firstElof, const pair<double,ll>& secondElof){
    return firstElof.second < secondElof.second;
}
//四方向への移動ベクトル
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};

struct edge{//グラフに使うヤツ
    ll from,to,cost;
};

typedef vector<vector<edge> > G;
ll gcd(ll a,ll b){
    if (a%b==0)return(b);
    else return(gcd(b,a%b));
}

int main() {
    ll l,r,d;
    cin >> l >> r >> d;
    ll ans=r/d-(l-1)/d;
    cout << ans << endl;
    return 0;
}