#include <stdio.h>
#include <iostream>
#include<fstream>
#include <cstdio>
using namespace std;

int readInt()
{
    int res = 0;
    char ch = 0;
    while(ch < '0') ch = getchar_unlocked();
    for(; ch >= '0'; ch = getchar_unlocked()) res = res * 10 + ch - '0';
    return res;

}

void writeInt(int v)
{
	//cout << v;

    char buf[14];
    int p = 0;
    if(v == 0) buf[p++] = 0;
    for(; v; v /= 10) buf[p++] = v % 10;
    while(p--) putchar_unlocked(buf[p] + '0');
}


int main()
{

    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);

    int min, max, n;
    n = readInt();

    int act[n];

  	act[0] = readInt();
 	act[1] = readInt();
 	min = 2 * act[0] - act[1];
 	max = act[0];

 	int combinazioniMinime = 1500000000;
int temp;
 	for(int i = 1; i <= n; i++)
 	{
 		if(i != 1 && i != n)
 	    	act[i] = readInt();
 		// trovo min e max
 		temp = min;
 		min = 2*act[i-1] - max;
 		max = 2*act[i-1] - temp;

 		if(max > act[i] && i!=n)
 			max = act[i];


 		temp = max - min + 1;
 		if(max - min + 1 < combinazioniMinime)
 			combinazioniMinime = temp;
	 }


	writeInt(combinazioniMinime);
    return 0;
}