#include<bits/stdc++.h>
#define int long long
using namespace std;
const int N=1e5+10;
const int INF=0x3f3f3f3f;
int a,b,c,d;
signed main()
{
	cin >> a >> b >> c >> d;
	int cnt=abs(a-b);
	int cnt1=abs(a-c);
	int cnt2=abs(a-d);
	int minn=INF;
	int minnn=min(cnt,min(cnt1,cnt2));
	if(cnt==minnn&&b<minn)minn=b;
	if(cnt1==minnn&&c<minn)minn=c;
	if(cnt2==minnn&&d<minn)minn=d;
	cout << minn;
	return 0;
}