#include <bits/stdc++.h>
using namespace std;
#define int long long

#define endl '\n'

#define ls (u << 1)

#define rs (u << 1 | 1)

int _max(int a, int b) { return a > b ? a : b; }
int _min(int a, int b) { return a < b ? a : b; }
double _max(double a, double b) { return a > b ? a : b; }
double _min(double a, double b) { return a < b ? a : b; }
int Gcd(int a, int b) { return __gcd(a, b); }
int Lcm(int a, int b) { return a * b / __gcd(a, b); }
int lowbit(int x) { return x & -x; }
int popcount(int x) { return __builtin_popcountll(x); }
int quickmi(int a, int b) {
    int ans = 1;
    while (b) {
        if (b & 1)
            ans *= a;
        a *= a;
        b >>= 1;
    }
    return ans;
}
signed main() {
    ios::sync_with_stdio(0);
    int A, K, L, R;
    cin >> A >> K >> L >> R;
    int s = 0;
    if (A > L && A < R) {
        s = A - ((A - L) / K) * K;
    } else if (A <= L) {
        s = A + (int)ceil((L - A) * 1.0 / K) * K;
    } else if (A >= R) {
        s = A - (A - L) / K * K;
    }
    cout << (R - s) / K + ((R - s) % K == 0) << endl;
}