#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

#define RREP(i,s,e) for (i = s; i >= e; i--)
#define rrep(i,n) RREP(i,n,0)
#define REP(i,s,e) for (i = s; i < e; i++)
#define rep(i,n) REP(i,0,n)
#define INF 1e8

typedef long long ll;

int main() {
    int d, h1, h2, h3;
    cin >> d >> h1 >> h2 >> h3;
    if (h2 == 0 && (h1 == 0 || h3 == 0))
        cout << -1 << endl;
    else if (h2 < min(h1,h3) || h2 > max(h1,h3))
        cout << 0 << endl;
    else
        cout << min(abs(h2-h1),abs(h2-h3)) / d + 1 << endl;
    return 0;
}