using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static string InputPattern = "Input5";

    static List<string> GetInputList()
    {
        var WillReturn = new List<string>();

        if (InputPattern == "Input1") {
            WillReturn.Add("1");
            WillReturn.Add("3");
            WillReturn.Add("3");
            WillReturn.Add("4");
            //1
            //真ん中の竹に1度魔法を唱えることで。条件を満たすことができます
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("411");
            WillReturn.Add("4");
            WillReturn.Add("1");
            WillReturn.Add("5");
            //0
            //魔法を使う必要がないこともあります
        }
        else if (InputPattern == "Input3") {
            WillReturn.Add("2");
            WillReturn.Add("3");
            WillReturn.Add("10");
            WillReturn.Add("12");
            //2
        }
        else if (InputPattern == "Input4") {
            WillReturn.Add("1");
            WillReturn.Add("0");
            WillReturn.Add("0");
            WillReturn.Add("0");
            //-1
            //魔法を使ってもどうしようもないこともあります
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

    static int D;

    static void Main()
    {
        List<string> InputList = GetInputList();
        D = int.Parse(InputList[0]);
        int H1 = int.Parse(InputList[1]);
        int H2 = int.Parse(InputList[2]);
        int H3 = int.Parse(InputList[3]);
        Console.WriteLine(DeriveAnswer(H1, H2, H3));
    }

    static int DeriveAnswer(int pH1, int pH2, int pH3)
    {
        int wkInt1 = DeriveMahouCnt1(pH1, pH2, pH3);
        int wkInt2 = DeriveMahouCnt2(pH1, pH2, pH3);

        if (wkInt1 == -1 && wkInt2 == -1) return -1;
        else if (wkInt1 == -1 && wkInt2 != -1) return wkInt2;
        else if (wkInt1 != -1 && wkInt2 == -1) return wkInt1;
        else return Math.Min(wkInt1, wkInt2);
    }

    //3本の竹全ての高さが互いに異なり、
    //真ん中の竹の高さが一番高い状態にする
    static int DeriveMahouCnt1(int pH1, int pH2, int pH3)
    {
        int MahouCnt = 0;

        if (pH2 <= pH1) {
            int wkCnt = (pH1 - pH2) / D + 1;
            ExecMahou(ref pH1, wkCnt);
            MahouCnt += wkCnt;
        }
        if (pH2 <= pH3) {
            int wkCnt = (pH3 - pH2) / D + 1;
            ExecMahou(ref pH3, wkCnt);
            MahouCnt += wkCnt;
        }

        if (pH1 == pH3) {
            ExecMahou(ref pH1, 1);
            MahouCnt++;
        }

        if (pH1 == pH2) return -1;
        if (pH1 == pH3) return -1;
        if (pH2 == pH3) return -1;
        if (pH2 <= pH1) return -1;
        if (pH2 <= pH3) return -1;
        return MahouCnt;
    }

    //3本の竹全ての高さが互いに異なり、
    //真ん中の竹の高さが一番低い状態にする
    static int DeriveMahouCnt2(int pH1, int pH2, int pH3)
    {
        int MahouCnt = 0;

        if (pH1 <= pH2) {
            int wkCnt = (pH2 - pH1) / D + 1;
            ExecMahou(ref pH2, wkCnt);
            MahouCnt += wkCnt;
        }
        if (pH3 <= pH2) {
            int wkCnt = (pH2 - pH3) / D + 1;
            ExecMahou(ref pH2, wkCnt);
            MahouCnt += wkCnt;
        }

        if (pH1 == pH3) {
            ExecMahou(ref pH1, 1);
            MahouCnt++;
        }

        if (pH1 == pH2) return -1;
        if (pH1 == pH3) return -1;
        if (pH2 == pH3) return -1;
        if (pH1 <= pH2) return -1;
        if (pH3 <= pH2) return -1;
        return MahouCnt;
    }

    //魔法をN回実行する
    static void ExecMahou(ref int pTarget, int pN)
    {
        pTarget = Math.Max(0, pTarget - pN * D);
    }
}