//author: camypaper
using System;
using System.Linq;
using System.Collections.Generic;
using System.Text.RegularExpressions;
using Debug = System.Diagnostics.Debug;
using SB = System.Text.StringBuilder;
using System.Numerics;
using Point = System.Numerics.Complex;
using static System.Math;
using C = System.Int32;

namespace Program {
    public class Solver {
        Random rnd = new Random(0);
        public void Solve() {
            var s = new int[] { ri, ri };
            var t = new int[] { ri, ri };
            var n = ri;
            var a = Enumerate(n, x => new int[] { ri, ri });
            double ans = (Abs(s[1] - t[1]) + Abs(s[0] - t[0])) * 100.0;
            if (s[0] == t[0] || s[1] == t[1]) {
                var flag = false;
                foreach (var p in a) {
                    for (int k = 0; k < 2; k++) {
                        flag |= s[k] == p[k] && p[k] == t[k]
                            && Min(s[k ^ 1], t[k ^ 1]) <= p[k ^ 1]
                            && p[k ^ 1] <= Max(s[k ^ 1], t[k ^ 1]);
                    }
                }
                if (flag) ans += 2 * PI * 10 / 2 - 20;
                Console.WriteLine(ans);
                return;
            }
            if (s[0] > t[0]) Swap(ref s, ref t);
            if (s[1] > t[1]) {
                s[1] *= -1; t[1] *= -1;
                for (int i = 0; i < n; i++)
                    a[i][1] *= -1;
            }
            //go right up
            a = a.OrderBy(x => x[0]).ToArray();
            var dp = Enumerate(n + 5, x => INF);
            dp[0] = s[1];
            foreach (var p in a) {
                if (p[0] < s[0]) continue;
                if (p[1] < s[1]) continue;
                if (p[0] > t[0]) continue;
                if (p[1] > t[1]) continue;
                Debug.WriteLine(p.AsJoinedString());
                var lb = dp.UpperBound(p[1]);
                dp[lb] = p[1];
            }
            for (int i = n; i >= 0; i--)
                if (dp[i] != INF) {
                    Debug.WriteLine($"!{i}");
                    if (i != Min(Abs(s[1] - t[1]), Abs(s[0] - t[0])) + 1)
                        ans += i * (20 * PI / 4 - 20);
                    else ans += (i - 1) * (20 * PI / 4 - 20) + 2 * PI * 10 / 2 - 20;
                    break;
                }
            Console.WriteLine(ans);
        }
        const long INF = 1L << 60;
        int ri => sc.Integer();
        long rl => sc.Long();
        double rd => sc.Double();
        string rs => sc.Scan();
        public IO.StreamScanner sc = new IO.StreamScanner(Console.OpenStandardInput());

        static IEnumerable<int> Rep(int n) => Enumerable.Range(0, n);
        static IEnumerable<int> RRep(int n) => Enumerable.Range(0, n).Reverse();
        static T[] Enumerate<T>(int n, Func<int, T> f) {
            var a = new T[n];
            for (int i = 0; i < a.Length; ++i) a[i] = f(i);
            return a;
        }
        static public void Swap<T>(ref T a, ref T b) { var tmp = a; a = b; b = tmp; }
    }
}

#region main
static class Ex {
    static public string AsString(this IEnumerable<char> ie) { return new string(ie.ToArray()); }
    static public string AsJoinedString<T>(this IEnumerable<T> ie, string st = " ") {
        return string.Join(st, ie);
    }
    static public void Main() {
        Console.SetOut(new Program.IO.Printer(Console.OpenStandardOutput()) { AutoFlush = false });
        var solver = new Program.Solver();
        solver.Solve();
        Console.Out.Flush();
    }
}
#endregion
#region Ex
namespace Program.IO {
    using System.IO;
    using System.Text;
    using System.Globalization;

    public class Printer : StreamWriter {
        public override IFormatProvider FormatProvider => CultureInfo.InvariantCulture;
        public Printer(Stream stream) : base(stream, new UTF8Encoding(false, true)) { }
    }

    public class StreamScanner {
        public StreamScanner(Stream stream) { str = stream; }

        public readonly Stream str;
        private readonly byte[] buf = new byte[1024];
        private int len, ptr;
        public bool isEof = false;

        private byte read() {
            if (isEof) return 0;
            if (ptr >= len) {
                ptr = 0;
                if ((len = str.Read(buf, 0, 1024)) <= 0) {
                    isEof = true;
                    return 0;
                }
            }
            return buf[ptr++];
        }

        public char Char() {
            byte b = 0;
            do b = read(); while ((b < 33 || 126 < b) && !isEof);
            return (char)b;
        }
        public string Scan() {
            var sb = new StringBuilder();
            for (var b = Char(); b >= 33 && b <= 126; b = (char)read()) sb.Append(b);
            return sb.ToString();
        }
        public string ScanLine() {
            var sb = new StringBuilder();
            for (var b = Char(); b != '\n' && b != 0; b = (char)read()) if (b != '\r') sb.Append(b);
            return sb.ToString();
        }
        public long Long() { return isEof ? long.MinValue : long.Parse(Scan()); }
        public int Integer() { return isEof ? int.MinValue : int.Parse(Scan()); }
        public double Double() { return isEof ? double.NaN : double.Parse(Scan(), CultureInfo.InvariantCulture); }
    }
}

#endregion
#region BinarySearch
public static partial class Algorithm {
    static int binarySearch<T>(IList<T> a, T v, IComparer<T> cmp, bool islb) {
        var l = 0;
        var r = a.Count - 1;
        while (l <= r) {
            var m = (l + r) / 2;
            var res = cmp.Compare(a[m], v);
            if (res < 0 || (res == 0 && !islb)) l = m + 1;
            else r = m - 1;
        }
        return l;
    }
    public static int LowerBound<T>(this IList<T> a, T v, Comparison<T> cmp) { return binarySearch(a, v, Comparer<T>.Create(cmp), true); }
    public static int LowerBound<T>(this IList<T> a, T v) { return binarySearch(a, v, Comparer<T>.Default, true); }
    public static int UpperBound<T>(this IList<T> a, T v, Comparison<T> cmp) { return binarySearch(a, v, Comparer<T>.Create(cmp), false); }
    public static int UpperBound<T>(this IList<T> a, T v) { return binarySearch(a, v, Comparer<T>.Default, false); }

}
#endregion

Measured memory_bytes: 36200