#include <bits/stdc++.h>
using namespace std;
template <class T>
void read(T& x) {
  cin >> x;
}
template <class H, class T>
void read(pair<H, T>& x) {
  read(x.first);
  read(x.second);
}
template <class A>
void read(vector<A>& v) {
  for (auto& x : v) read(x);
}
template <class H, class... T>
void read(H& h, T&... t) {
  read(h);
  read(t...);
}
string to_string(const char* c) { return (string)c; }
string to_string(char c) { return (string) "" + c; }
string to_string(string second) { return second; }
string to_string(bool b) { return b ? "True" : "False"; }
template <class A>
string to_string(vector<A> v) {
  string second;
  for (auto& x : v) second += to_string(x) + " ";
  return second;
}
template <class H, class... T>
string to_string(H& h, T&... t) {
  string second;
  second += to_string(h);
  second += " ";
  second += to_string(t...);
  return second;
}
void print(string second) { cout << second << "\n"; }
template <class... A>
void print(A... a) {
  print(to_string(a...));
}
int cdiv(int a, int b) { return a / b + !(a < 0 || a % b == 0); }
string tb(int x) {
  string ans;
  int c = x;
  for (int i = log2(x); i >= 0; --i) {
    if (pow(2, i) <= c) {
      ans += "1";
      c -= pow(2, i);
    } else {
      ans += "0";
    }
  }
  return ans;
}
bool ispr(int x) {
  if (x <= 1) {
    return false;
  }
  for (int i = 2; i <= sqrt(x); ++i) {
    if (x % i == 0) {
      return false;
    }
  }
  return true;
}
struct point {
  int x;
  int y;
};
const int MOD = 1e9 + 7;
const int MX = 2e5 + 5;
const long long INF = 1e18;
void solve() {
  double n, k;
  cin >> n >> k;
  double dist = 0;
  point prev;
  read(prev.x, prev.y);
  for (int i = 1; i < n; ++i) {
    point now;
    read(now.x, now.y);
    dist += sqrt((now.x - prev.x) * (now.x - prev.x) +
                 (now.y - prev.y) * (now.y - prev.y));
    prev = now;
  }
  printf("%.9f", (dist * k) / 50);
}
int main() {
  std::ios::sync_with_stdio(0);
  std::cin.tie(0);
  bool isT = 0;
  if (isT) {
    int t;
    cin >> t;
    while (t--) {
      solve();
    }
    return 0;
  }
  solve();
  return 0;
}
