#include <bits/stdc++.h>
using namespace std;
int tens[] = {1,      10,      100,      1000,      10000,
              100000, 1000000, 10000000, 100000000, 1000000000};
vector<int> nums;
void getc(int b, int start) {
  int c = 0;
  int ret = 0;
  int t = b;
  while (t) {
    t /= 10;
    c++;
  }
  int base = 0;
  int curr = 0;
  if (c == 10) --c;
  for (int digCount = 1; digCount <= c; ++digCount) {
    base = 0;
    for (int k = 0; k < digCount; ++k) base += 4 * tens[k];
    for (int i = 0; i < 1 << (digCount); ++i) {
      curr = base;
      for (int j = 0; j < digCount; ++j) {
        if (1 << j & i) curr += tens[j] * 3;
      }
      if (curr <= b) {
        if (curr >= start) nums.push_back(curr);
      } else
        return;
    }
  }
  return;
}
unsigned long long inter(unsigned long long l1, unsigned long long r1,
                         unsigned long long l2, unsigned long long r2) {
  unsigned long long l = l1 > l2 ? l1 : l2;
  unsigned long long r = r1 < r2 ? r1 : r2;
  return r >= l > 0 ? r - l + 1 : 0;
}
int main() {
  int vl, vr, pl, pr, k, r, l;
  scanf("%d%d%d%d%d", &vl, &vr, &pl, &pr, &k);
  r = max(vr, pr);
  l = min(vl, pl);
  getc(r, l);
  unsigned long long omega = (unsigned long long)(vr - vl + 1) * (pr - pl + 1);
  if (nums.size() < k) {
    puts("0");
    return 0;
  }
  unsigned long long c = 0;
  k--;
  unsigned long long l1, l2, r1, r2;
  for (int i = 0; i + k < nums.size(); ++i) {
    l1 = i > 0 ? nums[i - 1] + 1 : 0;
    r1 = nums[i];
    l2 = nums[i + k];
    r2 = i + k + 1 < nums.size() ? nums[i + k + 1] - 1 : 1000000001;
    c += inter(l1, r1, vl, vr) * inter(l2, r2, pl, pr);
    c += inter(l1, r1, pl, pr) * inter(l2, r2, vl, vr);
    if (k == 0 && (vl <= r1 && vr >= r1) && (pl <= r1 && pr >= r1)) c--;
  }
  printf("%.12lf\n", (double)c / omega);
  return 0;
}
