using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (t, sx, sy, tx, ty) = (c[0], c[1], c[2], c[3], c[4]);
        var min = 0;
        var max = t;
        while (max - min > 1)
        {
            var mid = (min + max) / 2;
            WriteLine($"? {mid}");
            c = NList;
            var slen = Len(sx, sy, c[0], c[1]);
            var tlen = Len(tx, ty, c[0], c[1]);
            if (slen == tlen)
            {
                WriteLine($"! {mid}");
                return;
            }
            if (slen < tlen) min = mid;
            else max = mid;
        }
        WriteLine($"! {min}");
    }
    static int Len(int ax, int ay, int bx, int by)
    {
        return Math.Abs(ax - bx) + Math.Abs(ay - by);
    }
}