func_code_string: #include <bits/stdc++.h>   using namespace std;   const int Max = 1000000100;   vector<long long> s;   void dfs(long long temp) {     if (temp > Max) {       return;     }     long long x = temp * 10 + 4;     if (temp > Max) {       return;     }     s.push_back(x);     dfs(x);     long long y = temp * 10 + 7;     if (temp > Max) {       return;     }     s.push_back(y);     dfs(y);   }   int main() {     dfs(0);     s.push_back(0);     sort(s.begin(), s.end());     long long l, r, x, y;     int n;     cin >> l >> r >> x >> y >> n;     long long temp = l > x ? x : l;     int i = lower_bound(s.begin(), s.end(), temp) - s.begin();     double sum = 0;     while (true) {       long long a = s[i - 1] + 1;       long long b = s[i];       long long c = s[i + n - 1];       long long d = s[i + n] - 1;       if (a > r && a > y) break;       if (c > r && c > y) break;       long long A = a > l ? a : l;       long long B = b < r ? b : r;       long long C = c > x ? c : x;       long long D = d < y ? d : y;       int shabi;       int z = 0;       if (n == 1 && B == C) {         int o = lower_bound(s.begin(), s.end(), B) - s.begin();         if (s[o] == B) z = 1;       }       if (z) shabi = D;       if (A <= B && C <= D) {         if (z)           sum += (double)(B - A) / (double)(r - l + 1) * (double)(D - C + 1) /                  (double)(y - x + 1);         else           sum += (double)(B - A + 1) / (double)(r - l + 1) * (double)(D - C + 1) /                  (double)(y - x + 1);       }       A = a > x ? a : x;       B = b < y ? b : y;       C = c > l ? c : l;       D = d < r ? d : r;       if (A <= B && C <= D) {         if (z)           sum += (double)(B - A + 1) / (double)(y - x + 1) * (double)(D - C) /                  (double)(r - l + 1);         else           sum += (double)(B - A + 1) / (double)(y - x + 1) * (double)(D - C + 1) /                  (double)(r - l + 1);       }       if (z) {         sum += (double)(shabi - A + 1) / (double)(y - x + 1) * (double)(1) /                (double)(r - l + 1);       }       i++;     }     printf( %.12lf , sum);     return 0;   }   