#include "bits/stdc++.h"
using namespace std;

#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

using ll = long long;
using LL = long long;


void solve(int TC) {
	ll n;
	long double p;
	ll l, r;

	cin >> n >> p >> l >> r;

	ll P = round(p * 1000000);

	ll LP = l * P;
	ll RP = r * P;

	ll L = LP / 1000000 + (LP % 1000000 != 0);
	ll R = RP / 1000000;


	if (L < 1) L = 1;
	if (R > n) R = n;

	ll ans = max(0ll, R - L + 1);

	cout << ans << "\n";

}

int32_t main() {
	cin.tie(0)->sync_with_stdio(0);
	cout << fixed << setprecision(10);

	int t = 1;
	// cin >> t;

	for (int i = 1; i <= t; i++) {
		solve(i);
	}
}