#include <bits/stdc++.h>
#define EPS 1e-9
#define INF 1070000000LL
#define MOD 1000000007LL
#define fir first
#define foreach(it,X) for(auto it=(X).begin();it!=(X).end();it++)
#define numa(x,a) for(auto x: a)
#define ite iterator
#define mp make_pair
#define rep(i,n) rep2(i,0,n)
#define rep2(i,m,n) for(int i=m;i<(n);i++)
#define pb push_back
#define pf push_front
#define sec second
#define sz(x) ((int)(x).size())
#define ALL( c ) (c).begin(), (c).end()
#define gcd(a,b) __gcd(a,b)
#define mem(x,n) memset(x,n,sizeof(x))
#define endl "\n"
using namespace std;
template <int POS, class TUPLE> void deploy(std::ostream &os, const TUPLE &tuple){}
template <int POS, class TUPLE, class H, class ...Ts> void deploy(std::ostream &os, const TUPLE &t){ os << (POS == 0 ? "" : ", ") << get<POS>(t); deploy<POS + 1, TUPLE, Ts...>(os, t); }
template <class T,class U> std::ostream& operator<<(std::ostream &os, std::pair<T,U> &p){ os << "(" << p.first <<", " << p.second <<")";return os; }
template <class T> std::ostream& operator<<(std::ostream &os, std::vector<T> &v){ int remain = v.size(); os << "{"; for(auto e: v) os << e << (--remain == 0 ? "}" : ", "); return os; }
template <class T> std::ostream& operator<<(std::ostream &os, std::set<T> &v){ int remain = v.size(); os << "{"; for(auto e: v) os << e << (--remain == 0 ? "}" : ", "); return os; }
template <class T, class K> std::ostream& operator<<(std::ostream &os, std::map<T, K> &mp){ int remain = mp.size(); os << "{"; for(auto e: mp) os << "(" << e.first << " -> " << e.second << ")" << (--remain == 0 ? "}" : ", "); return os; }
#define DEBUG1(var0) { std::cerr << (#var0) << "=" << (var0) << endl; }
#define DEBUG2(var0, var1) { std::cerr << (#var0) << "=" << (var0) << ", ";DEBUG1(var1); }
#define DEBUG3(var0, var1, var2) { std::cerr << (#var0) << "=" << (var0) << ", ";DEBUG2(var1,var2); }
#define DEBUG4(var0, var1, var2, var3) { std::cerr << (#var0) << "=" << (var0) << ", ";DEBUG3(var1,var2,var3); }
using ll = long long;
ll d;
ll calc(ll x, ll y){
  return floor((x - y) / d) + 1; 
}

int main()
{
  cin.tie(0);
  ios_base::sync_with_stdio(0);
  ll nums[3];
  cin >> d;
  rep(i,3){
    cin >> nums[i];
  }
  if (d == 0) {
    cout << -1 << endl;
    return 0;
  }
  if (nums[0] > nums[1]) {
    swap(nums[0],nums[1]);
  }
  if (nums[0] == nums[2]) {
    if (nums[0] != nums[1]) {
      cout << 1 << endl;
      return 0;
    }
    cout << 2 << endl;
    return 0;
  }
  if (nums[0] == nums[1]) {
    if (nums[0] - d >= 0 || nums[1] + d != nums[2]) {
      cout << 1 << endl;
      return 0;
    }
    cout << 2 << endl;
    return 0;
  }
  if (nums[2] == nums[1]) {
    cout << 1 << endl;
    return 0;
  }

  if (nums[0] < nums[1] && nums[1] < nums[2]) {
    ll a = floor(nums[2] - nums[1] / d) + 1;
    ll minh = nums[1] % d;
    if (nums[0] <= minh) {
      if (nums[0] + d == nums[2]) {
        a = min(a,2LL);
      }else if (nums[0] + d > nums[2]){
        a = min(a,1LL);
      }else{
        if (nums[0] + d > nums[1]) {
          a = min(a,1LL);
        }else if (nums[0] + d < nums[1]){
          a = min(a, (ll) floor((nums[1] - nums[0] + d) / d) + 2);
        }else{
          a = min(a,2LL);
        }
      }
    }else{
      a = min(a, (ll) floor(nums[1] - nums[0] / d) + 1);
    }
    cout << a << endl;
  }else{
    cout << 0 << endl;
  }
  
  
  

  
  
  return 0;
}