func_code_string: #include <bits/stdc++.h>   using namespace std;   bool comp(int a, int b) { return (a > b); }   int gcd(long long int a, long long int b) {     if (b == 0)       return a;     else       return gcd(b, a % b);   }   int main(void) {     int n, p;     cin >> n >> p;     int l[n], r[n], i;     long long int c, cp, l1, l2;     double ans = 0;     for (i = 0; i < n; ++i) cin >> l[i] >> r[i];     for (i = 0; i < n; ++i) {       l1 = r[i] - l[i] + 1;       l2 = r[(i - 1 + n) % n] - l[(i - 1 + n) % n] + 1;       c = r[i] / p - (l[i] - 1) / p;       cp = r[(i - 1 + n) % n] / p - (l[(i - 1 + n) % n] - 1) / p;       ans += (2000.0 * (c * l2 + cp * l1 - (c * cp))) / (l1 * l2);     }     printf( %.10lf , ans);     return 0;   }   