#include <bits/stdc++.h>   using namespace std;   long long int fun(long long int x, long long int y, long long int p) {     long long int s = x / p;     if (x % p) s++;     long long int e = y / p;     return e - s + 1;   }   void solve() {     long long int n, p;     cin >> n >> p;     vector<pair<long long int, long long int> > A(n);     for (int i = 0; i < n; i++) cin >> A[i].first >> A[i].second;     double ans = 0;     for (int i = 0; i < n; i++) {       long long int f = i, s = (i + 1 + n) % n;       long long int s1 = A[f].second - A[f].first + 1,                     s2 = A[s].second - A[s].first + 1;       long long int a = fun(A[f].first, A[f].second, p);       long long int b = fun(A[s].first, A[s].second, p);       double up = (s1 - a) * 1.0 * (s2 - b);       double d = s1 * 1.0 * s2 * 1.0;       up = (up * 1.0) / (d * 1.0);       double pro = 1.0 - 1.0 * up;       ans = ans * 1.0 + pro * 2000.0;     }     printf( %f n , ans);   }   int main() {     long long int t = 1;     while (t--) {       solve();     }     return 0;   }   