Problem: Petya loves lucky numbers. We all know that lucky numbers are the positive integers whose decimal representations contain only the lucky digits 4 and 7. For example, numbers 47, 744, 4 are lucky and 5, 17, 467 are not.

Petya and his friend Vasya play an interesting game. Petya randomly chooses an integer p from the interval [pl, pr] and Vasya chooses an integer v from the interval [vl, vr] (also randomly). Both players choose their integers equiprobably. Find the probability that the interval [min(v, p), max(v, p)] contains exactly k lucky numbers.

Input

The single line contains five integers pl, pr, vl, vr and k (1 ≤ pl ≤ pr ≤ 109, 1 ≤ vl ≤ vr ≤ 109, 1 ≤ k ≤ 1000).

Output

On the single line print the result with an absolute error of no more than 10 - 9.

Examples

Input

1 10 1 10 2


Output

0.320000000000


Input

5 6 8 10 1


Output

1.000000000000

Note

Consider that [a, b] denotes an interval of integers; this interval includes the boundaries. That is, <image>

In first case there are 32 suitable pairs: (1, 7), (1, 8), (1, 9), (1, 10), (2, 7), (2, 8), (2, 9), (2, 10), (3, 7), (3, 8), (3, 9), (3, 10), (4, 7), (4, 8), (4, 9), (4, 10), (7, 1), (7, 2), (7, 3), (7, 4), (8, 1), (8, 2), (8, 3), (8, 4), (9, 1), (9, 2), (9, 3), (9, 4), (10, 1), (10, 2), (10, 3), (10, 4). Total number of possible pairs is 10·10 = 100, so answer is 32 / 100.

In second case Petya always get number less than Vasya and the only lucky 7 is between this numbers, so there will be always 1 lucky number.

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
using namespace std;
const long long a[3000] = {
    0,          4,          7,          44,         47,         74,
    77,         444,        447,        474,        477,        744,
    747,        774,        777,        4444,       4447,       4474,
    4477,       4744,       4747,       4774,       4777,       7444,
    7447,       7474,       7477,       7744,       7747,       7774,
    7777,       44444,      44447,      44474,      44477,      44744,
    44747,      44774,      44777,      47444,      47447,      47474,
    47477,      47744,      47747,      47774,      47777,      74444,
    74447,      74474,      74477,      74744,      74747,      74774,
    74777,      77444,      77447,      77474,      77477,      77744,
    77747,      77774,      77777,      444444,     444447,     444474,
    444477,     444744,     444747,     444774,     444777,     447444,
    447447,     447474,     447477,     447744,     447747,     447774,
    447777,     474444,     474447,     474474,     474477,     474744,
    474747,     474774,     474777,     477444,     477447,     477474,
    477477,     477744,     477747,     477774,     477777,     744444,
    744447,     744474,     744477,     744744,     744747,     744774,
    744777,     747444,     747447,     747474,     747477,     747744,
    747747,     747774,     747777,     774444,     774447,     774474,
    774477,     774744,     774747,     774774,     774777,     777444,
    777447,     777474,     777477,     777744,     777747,     777774,
    777777,     4444444,    4444447,    4444474,    4444477,    4444744,
    4444747,    4444774,    4444777,    4447444,    4447447,    4447474,
    4447477,    4447744,    4447747,    4447774,    4447777,    4474444,
    4474447,    4474474,    4474477,    4474744,    4474747,    4474774,
    4474777,    4477444,    4477447,    4477474,    4477477,    4477744,
    4477747,    4477774,    4477777,    4744444,    4744447,    4744474,
    4744477,    4744744,    4744747,    4744774,    4744777,    4747444,
    4747447,    4747474,    4747477,    4747744,    4747747,    4747774,
    4747777,    4774444,    4774447,    4774474,    4774477,    4774744,
    4774747,    4774774,    4774777,    4777444,    4777447,    4777474,
    4777477,    4777744,    4777747,    4777774,    4777777,    7444444,
    7444447,    7444474,    7444477,    7444744,    7444747,    7444774,
    7444777,    7447444,    7447447,    7447474,    7447477,    7447744,
    7447747,    7447774,    7447777,    7474444,    7474447,    7474474,
    7474477,    7474744,    7474747,    7474774,    7474777,    7477444,
    7477447,    7477474,    7477477,    7477744,    7477747,    7477774,
    7477777,    7744444,    7744447,    7744474,    7744477,    7744744,
    7744747,    7744774,    7744777,    7747444,    7747447,    7747474,
    7747477,    7747744,    7747747,    7747774,    7747777,    7774444,
    7774447,    7774474,    7774477,    7774744,    7774747,    7774774,
    7774777,    7777444,    7777447,    7777474,    7777477,    7777744,
    7777747,    7777774,    7777777,    44444444,   44444447,   44444474,
    44444477,   44444744,   44444747,   44444774,   44444777,   44447444,
    44447447,   44447474,   44447477,   44447744,   44447747,   44447774,
    44447777,   44474444,   44474447,   44474474,   44474477,   44474744,
    44474747,   44474774,   44474777,   44477444,   44477447,   44477474,
    44477477,   44477744,   44477747,   44477774,   44477777,   44744444,
    44744447,   44744474,   44744477,   44744744,   44744747,   44744774,
    44744777,   44747444,   44747447,   44747474,   44747477,   44747744,
    44747747,   44747774,   44747777,   44774444,   44774447,   44774474,
    44774477,   44774744,   44774747,   44774774,   44774777,   44777444,
    44777447,   44777474,   44777477,   44777744,   44777747,   44777774,
    44777777,   47444444,   47444447,   47444474,   47444477,   47444744,
    47444747,   47444774,   47444777,   47447444,   47447447,   47447474,
    47447477,   47447744,   47447747,   47447774,   47447777,   47474444,
    47474447,   47474474,   47474477,   47474744,   47474747,   47474774,
    47474777,   47477444,   47477447,   47477474,   47477477,   47477744,
    47477747,   47477774,   47477777,   47744444,   47744447,   47744474,
    47744477,   47744744,   47744747,   47744774,   47744777,   47747444,
    47747447,   47747474,   47747477,   47747744,   47747747,   47747774,
    47747777,   47774444,   47774447,   47774474,   47774477,   47774744,
    47774747,   47774774,   47774777,   47777444,   47777447,   47777474,
    47777477,   47777744,   47777747,   47777774,   47777777,   74444444,
    74444447,   74444474,   74444477,   74444744,   74444747,   74444774,
    74444777,   74447444,   74447447,   74447474,   74447477,   74447744,
    74447747,   74447774,   74447777,   74474444,   74474447,   74474474,
    74474477,   74474744,   74474747,   74474774,   74474777,   74477444,
    74477447,   74477474,   74477477,   74477744,   74477747,   74477774,
    74477777,   74744444,   74744447,   74744474,   74744477,   74744744,
    74744747,   74744774,   74744777,   74747444,   74747447,   74747474,
    74747477,   74747744,   74747747,   74747774,   74747777,   74774444,
    74774447,   74774474,   74774477,   74774744,   74774747,   74774774,
    74774777,   74777444,   74777447,   74777474,   74777477,   74777744,
    74777747,   74777774,   74777777,   77444444,   77444447,   77444474,
    77444477,   77444744,   77444747,   77444774,   77444777,   77447444,
    77447447,   77447474,   77447477,   77447744,   77447747,   77447774,
    77447777,   77474444,   77474447,   77474474,   77474477,   77474744,
    77474747,   77474774,   77474777,   77477444,   77477447,   77477474,
    77477477,   77477744,   77477747,   77477774,   77477777,   77744444,
    77744447,   77744474,   77744477,   77744744,   77744747,   77744774,
    77744777,   77747444,   77747447,   77747474,   77747477,   77747744,
    77747747,   77747774,   77747777,   77774444,   77774447,   77774474,
    77774477,   77774744,   77774747,   77774774,   77774777,   77777444,
    77777447,   77777474,   77777477,   77777744,   77777747,   77777774,
    77777777,   444444444,  444444447,  444444474,  444444477,  444444744,
    444444747,  444444774,  444444777,  444447444,  444447447,  444447474,
    444447477,  444447744,  444447747,  444447774,  444447777,  444474444,
    444474447,  444474474,  444474477,  444474744,  444474747,  444474774,
    444474777,  444477444,  444477447,  444477474,  444477477,  444477744,
    444477747,  444477774,  444477777,  444744444,  444744447,  444744474,
    444744477,  444744744,  444744747,  444744774,  444744777,  444747444,
    444747447,  444747474,  444747477,  444747744,  444747747,  444747774,
    444747777,  444774444,  444774447,  444774474,  444774477,  444774744,
    444774747,  444774774,  444774777,  444777444,  444777447,  444777474,
    444777477,  444777744,  444777747,  444777774,  444777777,  447444444,
    447444447,  447444474,  447444477,  447444744,  447444747,  447444774,
    447444777,  447447444,  447447447,  447447474,  447447477,  447447744,
    447447747,  447447774,  447447777,  447474444,  447474447,  447474474,
    447474477,  447474744,  447474747,  447474774,  447474777,  447477444,
    447477447,  447477474,  447477477,  447477744,  447477747,  447477774,
    447477777,  447744444,  447744447,  447744474,  447744477,  447744744,
    447744747,  447744774,  447744777,  447747444,  447747447,  447747474,
    447747477,  447747744,  447747747,  447747774,  447747777,  447774444,
    447774447,  447774474,  447774477,  447774744,  447774747,  447774774,
    447774777,  447777444,  447777447,  447777474,  447777477,  447777744,
    447777747,  447777774,  447777777,  474444444,  474444447,  474444474,
    474444477,  474444744,  474444747,  474444774,  474444777,  474447444,
    474447447,  474447474,  474447477,  474447744,  474447747,  474447774,
    474447777,  474474444,  474474447,  474474474,  474474477,  474474744,
    474474747,  474474774,  474474777,  474477444,  474477447,  474477474,
    474477477,  474477744,  474477747,  474477774,  474477777,  474744444,
    474744447,  474744474,  474744477,  474744744,  474744747,  474744774,
    474744777,  474747444,  474747447,  474747474,  474747477,  474747744,
    474747747,  474747774,  474747777,  474774444,  474774447,  474774474,
    474774477,  474774744,  474774747,  474774774,  474774777,  474777444,
    474777447,  474777474,  474777477,  474777744,  474777747,  474777774,
    474777777,  477444444,  477444447,  477444474,  477444477,  477444744,
    477444747,  477444774,  477444777,  477447444,  477447447,  477447474,
    477447477,  477447744,  477447747,  477447774,  477447777,  477474444,
    477474447,  477474474,  477474477,  477474744,  477474747,  477474774,
    477474777,  477477444,  477477447,  477477474,  477477477,  477477744,
    477477747,  477477774,  477477777,  477744444,  477744447,  477744474,
    477744477,  477744744,  477744747,  477744774,  477744777,  477747444,
    477747447,  477747474,  477747477,  477747744,  477747747,  477747774,
    477747777,  477774444,  477774447,  477774474,  477774477,  477774744,
    477774747,  477774774,  477774777,  477777444,  477777447,  477777474,
    477777477,  477777744,  477777747,  477777774,  477777777,  744444444,
    744444447,  744444474,  744444477,  744444744,  744444747,  744444774,
    744444777,  744447444,  744447447,  744447474,  744447477,  744447744,
    744447747,  744447774,  744447777,  744474444,  744474447,  744474474,
    744474477,  744474744,  744474747,  744474774,  744474777,  744477444,
    744477447,  744477474,  744477477,  744477744,  744477747,  744477774,
    744477777,  744744444,  744744447,  744744474,  744744477,  744744744,
    744744747,  744744774,  744744777,  744747444,  744747447,  744747474,
    744747477,  744747744,  744747747,  744747774,  744747777,  744774444,
    744774447,  744774474,  744774477,  744774744,  744774747,  744774774,
    744774777,  744777444,  744777447,  744777474,  744777477,  744777744,
    744777747,  744777774,  744777777,  747444444,  747444447,  747444474,
    747444477,  747444744,  747444747,  747444774,  747444777,  747447444,
    747447447,  747447474,  747447477,  747447744,  747447747,  747447774,
    747447777,  747474444,  747474447,  747474474,  747474477,  747474744,
    747474747,  747474774,  747474777,  747477444,  747477447,  747477474,
    747477477,  747477744,  747477747,  747477774,  747477777,  747744444,
    747744447,  747744474,  747744477,  747744744,  747744747,  747744774,
    747744777,  747747444,  747747447,  747747474,  747747477,  747747744,
    747747747,  747747774,  747747777,  747774444,  747774447,  747774474,
    747774477,  747774744,  747774747,  747774774,  747774777,  747777444,
    747777447,  747777474,  747777477,  747777744,  747777747,  747777774,
    747777777,  774444444,  774444447,  774444474,  774444477,  774444744,
    774444747,  774444774,  774444777,  774447444,  774447447,  774447474,
    774447477,  774447744,  774447747,  774447774,  774447777,  774474444,
    774474447,  774474474,  774474477,  774474744,  774474747,  774474774,
    774474777,  774477444,  774477447,  774477474,  774477477,  774477744,
    774477747,  774477774,  774477777,  774744444,  774744447,  774744474,
    774744477,  774744744,  774744747,  774744774,  774744777,  774747444,
    774747447,  774747474,  774747477,  774747744,  774747747,  774747774,
    774747777,  774774444,  774774447,  774774474,  774774477,  774774744,
    774774747,  774774774,  774774777,  774777444,  774777447,  774777474,
    774777477,  774777744,  774777747,  774777774,  774777777,  777444444,
    777444447,  777444474,  777444477,  777444744,  777444747,  777444774,
    777444777,  777447444,  777447447,  777447474,  777447477,  777447744,
    777447747,  777447774,  777447777,  777474444,  777474447,  777474474,
    777474477,  777474744,  777474747,  777474774,  777474777,  777477444,
    777477447,  777477474,  777477477,  777477744,  777477747,  777477774,
    777477777,  777744444,  777744447,  777744474,  777744477,  777744744,
    777744747,  777744774,  777744777,  777747444,  777747447,  777747474,
    777747477,  777747744,  777747747,  777747774,  777747777,  777774444,
    777774447,  777774474,  777774477,  777774744,  777774747,  777774774,
    777774777,  777777444,  777777447,  777777474,  777777477,  777777744,
    777777747,  777777774,  777777777,  4444444444, 4444444447, 4444444474,
    4444444477, 4444444744, 4444444747, 4444444774, 4444444777, 4444447444,
    4444447447, 4444447474, 4444447477, 4444447744, 4444447747, 4444447774,
    4444447777, 4444474444, 4444474447, 4444474474, 4444474477, 4444474744,
    4444474747, 4444474774, 4444474777, 4444477444, 4444477447, 4444477474,
    4444477477, 4444477744, 4444477747, 4444477774, 4444477777, 4444744444,
    4444744447, 4444744474, 4444744477, 4444744744, 4444744747, 4444744774,
    4444744777, 4444747444, 4444747447, 4444747474, 4444747477, 4444747744,
    4444747747, 4444747774, 4444747777, 4444774444, 4444774447, 4444774474,
    4444774477, 4444774744, 4444774747, 4444774774, 4444774777, 4444777444,
    4444777447, 4444777474, 4444777477, 4444777744, 4444777747, 4444777774,
    4444777777, 4447444444, 4447444447, 4447444474, 4447444477, 4447444744,
    4447444747, 4447444774, 4447444777, 4447447444, 4447447447, 4447447474,
    4447447477, 4447447744, 4447447747, 4447447774, 4447447777, 4447474444,
    4447474447, 4447474474, 4447474477, 4447474744, 4447474747, 4447474774,
    4447474777, 4447477444, 4447477447, 4447477474, 4447477477, 4447477744,
    4447477747, 4447477774, 4447477777, 4447744444, 4447744447, 4447744474,
    4447744477, 4447744744, 4447744747, 4447744774, 4447744777, 4447747444,
    4447747447, 4447747474, 4447747477, 4447747744, 4447747747, 4447747774,
    4447747777, 4447774444, 4447774447, 4447774474, 4447774477, 4447774744,
    4447774747, 4447774774, 4447774777, 4447777444, 4447777447, 4447777474,
    4447777477, 4447777744, 4447777747, 4447777774, 4447777777, 4474444444,
    4474444447, 4474444474, 4474444477, 4474444744, 4474444747, 4474444774,
    4474444777, 4474447444, 4474447447, 4474447474, 4474447477, 4474447744,
    4474447747, 4474447774, 4474447777, 4474474444, 4474474447, 4474474474,
    4474474477, 4474474744, 4474474747, 4474474774, 4474474777, 4474477444,
    4474477447, 4474477474, 4474477477, 4474477744, 4474477747, 4474477774,
    4474477777, 4474744444, 4474744447, 4474744474, 4474744477, 4474744744,
    4474744747, 4474744774, 4474744777, 4474747444, 4474747447, 4474747474,
    4474747477, 4474747744, 4474747747, 4474747774, 4474747777, 4474774444,
    4474774447, 4474774474, 4474774477, 4474774744, 4474774747, 4474774774,
    4474774777, 4474777444, 4474777447, 4474777474, 4474777477, 4474777744,
    4474777747, 4474777774, 4474777777, 4477444444, 4477444447, 4477444474,
    4477444477, 4477444744, 4477444747, 4477444774, 4477444777, 4477447444,
    4477447447, 4477447474, 4477447477, 4477447744, 4477447747, 4477447774,
    4477447777, 4477474444, 4477474447, 4477474474, 4477474477, 4477474744,
    4477474747, 4477474774, 4477474777, 4477477444, 4477477447, 4477477474,
    4477477477, 4477477744, 4477477747, 4477477774, 4477477777, 4477744444,
    4477744447, 4477744474, 4477744477, 4477744744, 4477744747, 4477744774,
    4477744777, 4477747444, 4477747447, 4477747474, 4477747477, 4477747744,
    4477747747, 4477747774, 4477747777, 4477774444, 4477774447, 4477774474,
    4477774477, 4477774744, 4477774747, 4477774774, 4477774777, 4477777444,
    4477777447, 4477777474, 4477777477, 4477777744, 4477777747, 4477777774,
    4477777777, 4744444444, 4744444447, 4744444474, 4744444477, 4744444744,
    4744444747, 4744444774, 4744444777, 4744447444, 4744447447, 4744447474,
    4744447477, 4744447744, 4744447747, 4744447774, 4744447777, 4744474444,
    4744474447, 4744474474, 4744474477, 4744474744, 4744474747, 4744474774,
    4744474777, 4744477444, 4744477447, 4744477474, 4744477477, 4744477744,
    4744477747, 4744477774, 4744477777, 4744744444, 4744744447, 4744744474,
    4744744477, 4744744744, 4744744747, 4744744774, 4744744777, 4744747444,
    4744747447, 4744747474, 4744747477, 4744747744, 4744747747, 4744747774,
    4744747777, 4744774444, 4744774447, 4744774474, 4744774477, 4744774744,
    4744774747, 4744774774, 4744774777, 4744777444, 4744777447, 4744777474,
    4744777477, 4744777744, 4744777747, 4744777774, 4744777777, 4747444444,
    4747444447, 4747444474, 4747444477, 4747444744, 4747444747, 4747444774,
    4747444777, 4747447444, 4747447447, 4747447474, 4747447477, 4747447744,
    4747447747, 4747447774, 4747447777, 4747474444, 4747474447, 4747474474,
    4747474477, 4747474744, 4747474747, 4747474774, 4747474777, 4747477444,
    4747477447, 4747477474, 4747477477, 4747477744, 4747477747, 4747477774,
    4747477777, 4747744444, 4747744447, 4747744474, 4747744477, 4747744744,
    4747744747, 4747744774, 4747744777, 4747747444, 4747747447, 4747747474,
    4747747477, 4747747744, 4747747747, 4747747774, 4747747777, 4747774444,
    4747774447, 4747774474, 4747774477, 4747774744, 4747774747, 4747774774,
    4747774777, 4747777444, 4747777447, 4747777474, 4747777477, 4747777744,
    4747777747, 4747777774, 4747777777, 4774444444, 4774444447, 4774444474,
    4774444477, 4774444744, 4774444747, 4774444774, 4774444777, 4774447444,
    4774447447, 4774447474, 4774447477, 4774447744, 4774447747, 4774447774,
    4774447777, 4774474444, 4774474447, 4774474474, 4774474477, 4774474744,
    4774474747, 4774474774, 4774474777, 4774477444, 4774477447, 4774477474,
    4774477477, 4774477744, 4774477747, 4774477774, 4774477777, 4774744444,
    4774744447, 4774744474, 4774744477, 4774744744, 4774744747, 4774744774,
    4774744777, 4774747444, 4774747447, 4774747474, 4774747477, 4774747744,
    4774747747, 4774747774, 4774747777, 4774774444, 4774774447, 4774774474,
    4774774477, 4774774744, 4774774747, 4774774774, 4774774777, 4774777444,
    4774777447, 4774777474, 4774777477, 4774777744, 4774777747, 4774777774,
    4774777777, 4777444444, 4777444447, 4777444474, 4777444477, 4777444744,
    4777444747, 4777444774, 4777444777, 4777447444, 4777447447, 4777447474,
    4777447477, 4777447744, 4777447747, 4777447774, 4777447777, 4777474444,
    4777474447, 4777474474, 4777474477, 4777474744, 4777474747, 4777474774,
    4777474777, 4777477444, 4777477447, 4777477474, 4777477477, 4777477744,
    4777477747, 4777477774, 4777477777, 4777744444, 4777744447, 4777744474,
    4777744477, 4777744744, 4777744747, 4777744774, 4777744777, 4777747444,
    4777747447, 4777747474, 4777747477, 4777747744, 4777747747, 4777747774,
    4777747777, 4777774444, 4777774447, 4777774474, 4777774477, 4777774744,
    4777774747, 4777774774, 4777774777, 4777777444, 4777777447, 4777777474,
    4777777477, 4777777744, 4777777747, 4777777774, 4777777777, 7444444444,
    7444444447, 7444444474, 7444444477, 7444444744, 7444444747, 7444444774,
    7444444777, 7444447444, 7444447447, 7444447474, 7444447477, 7444447744,
    7444447747, 7444447774, 7444447777, 7444474444, 7444474447, 7444474474,
    7444474477, 7444474744, 7444474747, 7444474774, 7444474777, 7444477444,
    7444477447, 7444477474, 7444477477, 7444477744, 7444477747, 7444477774,
    7444477777, 7444744444, 7444744447, 7444744474, 7444744477, 7444744744,
    7444744747, 7444744774, 7444744777, 7444747444, 7444747447, 7444747474,
    7444747477, 7444747744, 7444747747, 7444747774, 7444747777, 7444774444,
    7444774447, 7444774474, 7444774477, 7444774744, 7444774747, 7444774774,
    7444774777, 7444777444, 7444777447, 7444777474, 7444777477, 7444777744,
    7444777747, 7444777774, 7444777777, 7447444444, 7447444447, 7447444474,
    7447444477, 7447444744, 7447444747, 7447444774, 7447444777, 7447447444,
    7447447447, 7447447474, 7447447477, 7447447744, 7447447747, 7447447774,
    7447447777, 7447474444, 7447474447, 7447474474, 7447474477, 7447474744,
    7447474747, 7447474774, 7447474777, 7447477444, 7447477447, 7447477474,
    7447477477, 7447477744, 7447477747, 7447477774, 7447477777, 7447744444,
    7447744447, 7447744474, 7447744477, 7447744744, 7447744747, 7447744774,
    7447744777, 7447747444, 7447747447, 7447747474, 7447747477, 7447747744,
    7447747747, 7447747774, 7447747777, 7447774444, 7447774447, 7447774474,
    7447774477, 7447774744, 7447774747, 7447774774, 7447774777, 7447777444,
    7447777447, 7447777474, 7447777477, 7447777744, 7447777747, 7447777774,
    7447777777, 7474444444, 7474444447, 7474444474, 7474444477, 7474444744,
    7474444747, 7474444774, 7474444777, 7474447444, 7474447447, 7474447474,
    7474447477, 7474447744, 7474447747, 7474447774, 7474447777, 7474474444,
    7474474447, 7474474474, 7474474477, 7474474744, 7474474747, 7474474774,
    7474474777, 7474477444, 7474477447, 7474477474, 7474477477, 7474477744,
    7474477747, 7474477774, 7474477777, 7474744444, 7474744447, 7474744474,
    7474744477, 7474744744, 7474744747, 7474744774, 7474744777, 7474747444,
    7474747447, 7474747474, 7474747477, 7474747744, 7474747747, 7474747774,
    7474747777, 7474774444, 7474774447, 7474774474, 7474774477, 7474774744,
    7474774747, 7474774774, 7474774777, 7474777444, 7474777447, 7474777474,
    7474777477, 7474777744, 7474777747, 7474777774, 7474777777, 7477444444,
    7477444447, 7477444474, 7477444477, 7477444744, 7477444747, 7477444774,
    7477444777, 7477447444, 7477447447, 7477447474, 7477447477, 7477447744,
    7477447747, 7477447774, 7477447777, 7477474444, 7477474447, 7477474474,
    7477474477, 7477474744, 7477474747, 7477474774, 7477474777, 7477477444,
    7477477447, 7477477474, 7477477477, 7477477744, 7477477747, 7477477774,
    7477477777, 7477744444, 7477744447, 7477744474, 7477744477, 7477744744,
    7477744747, 7477744774, 7477744777, 7477747444, 7477747447, 7477747474,
    7477747477, 7477747744, 7477747747, 7477747774, 7477747777, 7477774444,
    7477774447, 7477774474, 7477774477, 7477774744, 7477774747, 7477774774,
    7477774777, 7477777444, 7477777447, 7477777474, 7477777477, 7477777744,
    7477777747, 7477777774, 7477777777, 7744444444, 7744444447, 7744444474,
    7744444477, 7744444744, 7744444747, 7744444774, 7744444777, 7744447444,
    7744447447, 7744447474, 7744447477, 7744447744, 7744447747, 7744447774,
    7744447777, 7744474444, 7744474447, 7744474474, 7744474477, 7744474744,
    7744474747, 7744474774, 7744474777, 7744477444, 7744477447, 7744477474,
    7744477477, 7744477744, 7744477747, 7744477774, 7744477777, 7744744444,
    7744744447, 7744744474, 7744744477, 7744744744, 7744744747, 7744744774,
    7744744777, 7744747444, 7744747447, 7744747474, 7744747477, 7744747744,
    7744747747, 7744747774, 7744747777, 7744774444, 7744774447, 7744774474,
    7744774477, 7744774744, 7744774747, 7744774774, 7744774777, 7744777444,
    7744777447, 7744777474, 7744777477, 7744777744, 7744777747, 7744777774,
    7744777777, 7747444444, 7747444447, 7747444474, 7747444477, 7747444744,
    7747444747, 7747444774, 7747444777, 7747447444, 7747447447, 7747447474,
    7747447477, 7747447744, 7747447747, 7747447774, 7747447777, 7747474444,
    7747474447, 7747474474, 7747474477, 7747474744, 7747474747, 7747474774,
    7747474777, 7747477444, 7747477447, 7747477474, 7747477477, 7747477744,
    7747477747, 7747477774, 7747477777, 7747744444, 7747744447, 7747744474,
    7747744477, 7747744744, 7747744747, 7747744774, 7747744777, 7747747444,
    7747747447, 7747747474, 7747747477, 7747747744, 7747747747, 7747747774,
    7747747777, 7747774444, 7747774447, 7747774474, 7747774477, 7747774744,
    7747774747, 7747774774, 7747774777, 7747777444, 7747777447, 7747777474,
    7747777477, 7747777744, 7747777747, 7747777774, 7747777777, 7774444444,
    7774444447, 7774444474, 7774444477, 7774444744, 7774444747, 7774444774,
    7774444777, 7774447444, 7774447447, 7774447474, 7774447477, 7774447744,
    7774447747, 7774447774, 7774447777, 7774474444, 7774474447, 7774474474,
    7774474477, 7774474744, 7774474747, 7774474774, 7774474777, 7774477444,
    7774477447, 7774477474, 7774477477, 7774477744, 7774477747, 7774477774,
    7774477777, 7774744444, 7774744447, 7774744474, 7774744477, 7774744744,
    7774744747, 7774744774, 7774744777, 7774747444, 7774747447, 7774747474,
    7774747477, 7774747744, 7774747747, 7774747774, 7774747777, 7774774444,
    7774774447, 7774774474, 7774774477, 7774774744, 7774774747, 7774774774,
    7774774777, 7774777444, 7774777447, 7774777474, 7774777477, 7774777744,
    7774777747, 7774777774, 7774777777, 7777444444, 7777444447, 7777444474,
    7777444477, 7777444744, 7777444747, 7777444774, 7777444777, 7777447444,
    7777447447, 7777447474, 7777447477, 7777447744, 7777447747, 7777447774,
    7777447777, 7777474444, 7777474447, 7777474474, 7777474477, 7777474744,
    7777474747, 7777474774, 7777474777, 7777477444, 7777477447, 7777477474,
    7777477477, 7777477744, 7777477747, 7777477774, 7777477777, 7777744444,
    7777744447, 7777744474, 7777744477, 7777744744, 7777744747, 7777744774,
    7777744777, 7777747444, 7777747447, 7777747474, 7777747477, 7777747744,
    7777747747, 7777747774, 7777747777, 7777774444, 7777774447, 7777774474,
    7777774477, 7777774744, 7777774747, 7777774774, 7777774777, 7777777444,
    7777777447, 7777777474, 7777777477, 7777777744, 7777777747, 7777777774,
    7777777777};
long long cnt, summ, x, y, xx, yy, pl, pr, vl, vr, k, l, r, tmpx, tmpy, ll, rr,
    n;
bool flag;
long long max(long long a, long long b) {
  if (a > b)
    return a;
  else
    return b;
}
long long min(long long a, long long b) {
  if (a > b)
    return b;
  else
    return a;
}
int main() {
  cin >> pl >> pr >> vl >> vr >> k;
  n = 2046;
  xx = min(pl, vl);
  yy = max(pr, vr);
  summ = (pr - pl + 1) * (vr - vl + 1);
  flag = true;
  for (int i = 1; i <= n; i++) {
    if (a[i] >= xx) {
      tmpx = i;
      flag = false;
      break;
    }
  }
  if (flag == true) tmpx = n;
  flag = true;
  for (int i = 1; i <= n; i++) {
    if (a[i] > yy) {
      tmpy = i - 1;
      flag = false;
      break;
    }
  }
  if (flag == true) tmpy = n;
  cnt = 0;
  for (int i = tmpx; i <= tmpy - k + 1; i++) {
    l = max(pl, a[i - 1] + 1);
    ll = min(pr, a[i]);
    rr = min(vr, a[i + k] - 1);
    r = max(vl, a[i + k - 1]);
    if (ll - l + 1 >= 0 && rr - r + 1 >= 0) cnt += (ll - l + 1) * (rr - r + 1);
    if (ll == r) cnt--;
    l = max(vl, a[i - 1] + 1);
    ll = min(vr, a[i]);
    rr = min(pr, a[i + k] - 1);
    r = max(pl, a[i + k - 1]);
    if (ll - l + 1 >= 0 && rr - r + 1 >= 0) cnt += (ll - l + 1) * (rr - r + 1);
  }
  double anss;
  if (cnt > summ) cnt = summ;
  anss = double(cnt) / double(summ);
  printf("%.10llf", anss);
  return 0;
}