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 <random>
#include <chrono>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ll long long int
#define ld long double
#define ull unsigned ll
#define pb push_back
#define popb pop_back
#define mt make_tuple
#define eb emplace_back
#define mp make_pair
#define ff first
#define ss second
#define pii pair <int,int>
#define piii pair <pii,int>
#define piiii pair <pii,pii>
#define pll pair <ll,ll>
#define plll pair <pair <ll, ll>, ll>
#define rep0(i,n) for(ll i=0;i<(ll)n;i++)
#define rep1(i,n) for(ll i=1;i<=(ll)n;i++)
#define rep(i,x,y) for(ll i=(ll)x;i<=(ll)y;i++)
#define reprev(i,n) for(ll i=(ll)n;i>=0;i--)
#define all(c) c.begin(),c.end()
#define print(a) rep0(i,a.size()) cout << a[i] << " "
#define hi() cout << "\nHello, I am error. Can you find me? :):):)\n"
#define Randomize mt19937 rng(chrono::steady_clock::now().time_since_eppoch().count())
 
using namespace __gnu_pbds;
using namespace std;
using ordered_set =  tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>;

// FOR DEBUGGING
vector<string> vec_splitter(string s) {
	s += ',';
	vector<string> res;
	while(!s.empty()) {
		res.push_back(s.substr(0, s.find(',')));
		s = s.substr(s.find(',') + 1);
	}
	return res;
}

void debug_out(
vector<string> __attribute__ ((unused)) args,
__attribute__ ((unused)) int idx, 
__attribute__ ((unused)) int LINE_NUM) { cerr << endl; } 
template <typename Head, typename... Tail>
void debug_out(vector<string> args, int idx, int LINE_NUM, Head H, Tail... T) {
	if(idx > 0) cerr << ", ";
	else cerr << "Line(" << LINE_NUM << ") ";
	stringstream ss; ss << H;
	cerr << args[idx] << " = " << ss.str();
	debug_out(args, idx + 1, LINE_NUM, T...);
}

#ifndef XOX
#define debug(...) debug_out(vec_splitter(#__VA_ARGS__), 0, __LINE__, __VA_ARGS__)
#else
#define debug(...) 42
#endif

const int mod = 1e9+7;
const long double pi = acos(-1);
const ll INF = 1e15;

ll power(ll x, ll y){
	x %= mod;
	ll ans = 1;
	while(y){
		if(y&1) ans = (ans*x)%mod;
		y /= 2;
		x = (x*x)%mod;
	}
	return ans;
}

void solve(){

	int l,r,d;
	cin >> l >> r >> d;
	if(d==1){
		cout << r-l+1;
		return;
	}
	int ans = 0;
	if(l%d==0){
		ans++;
		l++;
	}
	if(r%d==0){
		ans++;
		r--;
	}
	ans += r/d - l/d;
	cout << ans;

	return;
}

int main(){

	ios::sync_with_stdio(0);
	cin.tie(0); cout.tie(0);

	int TC = 1,t = 0;
	// cin >> TC;
	while(t++ < TC){
		// cout << "Case #" << t << ": ";
		solve();
		// cout << "\n";
	}

	cerr << "Time : " << 1000 * ((double)clock()) / (double)CLOCKS_PER_SEC << "ms\n";

	return 0; 
}