#include <iostream>
#include <vector>
#include <cstdio>
#include <sstream>
#include <map>
#include <string>
#include <algorithm>
#include <queue>
#include <cmath>
#include <set>
using namespace std;

bool check(vector<long long>& h){
	if(h[0] == h[1] || h[1] == h[2] || h[2] == h[0]) return false;
	if(h[1] > h[0] && h[1] > h[2]) return true;
	if(h[1] < h[0] && h[1] < h[2]) return true;
	return false;
}

int main(){
	long long d;
	cin >> d;

	vector<long long> h(3);
	for(int i=0; i<3; i++){
		cin >> h[i];
	}

	if(check(h)){
		cout << 0 << endl;
		return 0;
	}


	long long ans = -1;

	{	// h[1] > h[0],h[2]

		vector<long long> h_ = h;
		long long tmp = 0;

		long long lb = -1;
		long long ub = 1e10;
		while(ub-lb>1){
			long long mid = (ub+lb)/2;
			long long len = max(0LL, h_[0] - d*mid);
			if(len >= h_[1]){
				lb = mid;
			}else{
				ub = mid;
			}
		}

		h_[0] = max(0LL, h_[0] - d*ub);
		tmp += ub;


		lb = -1;
		ub = 1e10;
		while(ub-lb>1){
			long long mid = (ub+lb)/2;
			long long len = max(0LL, h_[2] - d*mid);
			if(len >= h_[1]){
				lb = mid;
			}else{
				ub = mid;
			}
		}

		h_[2] = max(0LL, h_[2] - d*ub);
		tmp += ub;

		if(h_[0] == h_[2]){
			h_[0] = max(0LL, h_[0] - d*ub);
			tmp++;
		}

		if(check(h_)){
			ans = tmp;
		}
	}

	{	// h[1] < h[0],h[2]

		vector<long long> h_ = h;
		long long tmp = 0;

		long long lb = -1;
		long long ub = 1e10;

		while(ub-lb>1){
			long long mid = (ub+lb)/2;
			long long len = max(0LL, h_[1] - d*mid);
			if(len >= h_[0] || len >= h_[2]){
				lb = mid;
			}else{
				ub = mid;
			}
		}

		h_[1] = max(0LL, h_[1] - d*ub);
		tmp += ub;

		if(h_[0] == h_[2]){
			h_[0] = max(0LL, h_[0] - d*ub);
			tmp++;
		}

		if(h_[0] == h_[1]){
			h_[1] = max(0LL, h_[1] - d*ub);
			tmp++;
		}

		if(check(h_)){
			if(ans == -1){
				ans = tmp;
			}else{
				ans = min(ans, tmp);
			}
		}
	}

	cout << ans << endl;

	return 0;
}