#include <bits/stdc++.h>
#define int long long

using pii = std::pair<int, int>;
using tuu = std::tuple<int, int, int>;
#define pb push_back

using std::cin, std::cout, std::string, std::vector;
int read(int x = 0, int f = 0, char ch = getchar()) {
    while (ch < 48 or 57 < ch) f = ch == 45, ch = getchar();
    while (48 <= ch and ch <= 57) x = x * 10 + ch - 48, ch = getchar();
    return f ? -x : x;
}
const int N = 1e6 + 5;
// const int INF = 1e18;
int n, m, a[N];
void solve() {
    int A = read(), K = read(), L = read(), R = read();
    int P = 0;
    if (A >= L)
        A = A - K * ((A - L) / K);
    else if (A <= L)
        A = A + K * ((L - A) / K);
    int ans = (R - A) / K + (((R - A) % K == 0));
    // printf("%lld %lld %lld %lld\n", A, K, L, R);
    cout << ans;
}

signed main() {
#ifndef ONLINE_JUDGE
    freopen("D.in", "r", stdin);
#endif
    for (int T = 1; T--; solve())
        ;
    return 0;
}