func_code_string: #include <bits/stdc++.h>   using namespace std;   long long labs(long long a) { return a < 0 ? (-a) : a; }   long long max(long long a, long long b) { return a > b ? a : b; }   long long min(long long a, long long b) { return a < b ? a : b; }   vector<long long> v;   long long Intersect(pair<long long, long long> p1,                       pair<long long, long long> p2) {     pair<long long, long long> res;     res.first = max(p1.first, p2.first);     res.second = min(p1.second, p2.second);     if (res.first > res.second) return 0;     return res.second - res.first + 1;   }   long long Len(pair<long long, long long> p) { return p.second - p.first + 1; }   int main() {     pair<long long, long long> p1, p2;     int k;     cin >> p1.first >> p1.second >> p2.first >> p2.second >> k;     for (int len = 1; len < 11; len++) {       for (long long mask = 0; mask < (1 << len); mask++) {         long long a = mask;         long long num = 0;         for (int(i) = 0; (i) < (len); (i)++) {           num = num * 10 + (a % 2 ? 4 : 7);           a /= 2;         }         v.push_back(num);       }     }     v.push_back(0);     sort((v).begin(), (v).end());     while (v[v.size() - 2] > 1000000000) v.pop_back();     int i1 = 1;     int i2 = k;     double res = 0;     for (; i2 < v.size() - 1; i1++, i2++) {       pair<long long, long long> g1 = make_pair(v[i1 - 1] + 1, v[i1]);       pair<long long, long long> g2 = make_pair(v[i2], v[i2 + 1] - 1);       res += (double)Intersect(p1, g1) / (double)Len(p1) *              (double)Intersect(p2, g2) / (double)Len(p2);       res += (double)Intersect(p2, g1) / (double)Len(p2) *              (double)Intersect(p1, g2) / (double)Len(p1);       if (k == 1) {         pair<long long, long long> pc = make_pair(v[i1], v[i1]);         res -= (double)Intersect(p2, pc) / (double)Len(p2) *                (double)Intersect(p1, pc) / (double)Len(p1);       }     }     printf( %.10f , res);     return 0;   }   