func_code_string: #include <bits/stdc++.h>   int cmp(const void *a, const void *b) { return *((int *)a) - *((int *)b); }   int maximum(int a, int b) {     if (a > b) {       return a;     } else {       return b;     }   }   int minimum(int a, int b) {     if (a < b) {       return a;     } else {       return b;     }   }   int main() {     int a[2000];     int p = 0, q = 1, x = 1, i, j;     int pl, pr, vl, vr, k;     long long c = 0, d;     a[0] = 0;     for (i = 0; i < 9; i++) {       for (j = p; j < q; j++) {         a[x++] = a[j] * 10 + 4;         a[x++] = a[j] * 10 + 7;       }       p = q;       q = x;     }     qsort(a, x, sizeof(int), cmp);     a[x] = 1000000001;     scanf( %d %d %d %d %d , &pl, &pr, &vl, &vr, &k);     d = (long long)(pr - pl + 1) * (vr - vl + 1);     for (i = 1; i <= x - k; i++) {       if (pl <= a[i] && vr >= a[i + k - 1]) {         int s1 = minimum(a[i], pr);         int s2 = maximum(a[i - 1] + 1, pl);         int t1 = maximum(a[i + k - 1], vl);         int t2 = minimum(a[i + k] - 1, vr);         if (s1 - s2 >= 0 && t2 - t1 >= 0) {           c += (long long)(s1 - s2 + 1) * (t2 - t1 + 1);         }       }       if (vl <= a[i] && pr >= a[i + k - 1]) {         int s1 = minimum(a[i], vr);         int s2 = maximum(a[i - 1] + 1, vl);         int t1 = maximum(a[i + k - 1], pl);         int t2 = minimum(a[i + k] - 1, pr);         if (s1 - s2 >= 0 && t2 - t1 >= 0) {           c += (long long)(s1 - s2 + 1) * (t2 - t1 + 1);         }       }     }     if (k == 1) {       for (i = 1; i < x; i++) {         if (pl <= a[i] && pr >= a[i] && vl <= a[i] && vr >= a[i]) c--;       }     }     printf( %.20lf n , (double)c / d);     return 0;   }   