#include <bits/stdc++.h>
using namespace std;
__int128 a, k, l, r, na;
void out(__int128 num) {
    if (num < 0) {
        putchar('-');
        out(-1 * num);
        return;
    }
    if (num == 0)
        return;
    out(num / 10);
    putchar(num % 10 + '0');
    return;
}
__int128 read() {
    bool flag = 0;
    __int128 rt = 0;
    char c = getchar();
    while (c == ' ' || c == '\n') c = getchar();
    if (c == '-') {
        flag = 1;
        c = getchar();
    }
    while (c >= '0' && c <= '9') {
        rt *= 10;
        rt += c - '0';
        c = getchar();
    }
    if (flag)
        return -1 * rt;
    return rt;
}
int main() {
    a = read();
    k = read();
    l = read();
    r = read();
    na = a;
    if (na > l) {
        na -= ((na - l) / k * k);
    }
    if (na < l) {
        na += ((l - na) / k * k);
        if (na < l)
            na += k;
    }
    if (na > r) {
        cout << 0;
        return 0;
    }
    //	out(na);
    __int128 ans = (r - na) / k + 1;
    out(ans);
    return 0;
}