#include <bits/stdc++.h>
using namespace std;
void c_p_c() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
}
long long modexp(long long a, long long b, long long c) {
  long long ans = 1;
  a %= c;
  if (a == 0) {
    return 0;
  }
  while (b > 0) {
    if (b % 2) {
      ans = (ans * a) % c;
    }
    b /= 2;
    a = (a * a) % c;
  }
  return ans;
}
long long fact(long long n) {
  long long res = 1;
  for (long long i = 2; i <= n; i++) res = res * i;
  return res;
}
long long power(long long x, long long y, long long p) {
  long long res = 1;
  x = x % p;
  while (y > 0) {
    if (y & 1) res = (res * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return res;
}
long long modInverse(long long n, long long p) { return power(n, p - 2, p); }
long long nCrModPFermat(long long n, long long r, long long p) {
  if (n < r) return 0;
  if (r == 0) return 1;
  unsigned long long fac[n + 1];
  fac[0] = 1;
  for (int i = 1; i <= n; i++) fac[i] = (fac[i - 1] * i) % p;
  return (fac[n] * modInverse(fac[r], p) % p * modInverse(fac[n - r], p) % p) %
         p;
}
long long nPr(long long n, long long r) { return fact(n) / fact(n - r); }
vector<long long> createsieve(long long n) {
  vector<long long> primes;
  vector<long long> sieve(n + 1);
  for (long long i = 2; i * i <= n; i++) {
    if (sieve[i] == 0) {
      for (long long j = i * i; j <= n; j += i) {
        sieve[j] = 1;
      }
    }
  }
  for (long long i = 2; i <= n; i++) {
    if (sieve[i] == 0) {
      primes.push_back(i);
    }
  }
  return primes;
}
int convertBinaryToDecimal(long long n) {
  int decimalNumber = 0, i = 0, remainder;
  while (n != 0) {
    remainder = n % 10;
    n /= 10;
    decimalNumber += remainder * pow(2, i);
    ++i;
  }
  return decimalNumber;
}
int gcd(int a, int b) {
  if (b > a) return gcd(b, a);
  return b == 0 ? a : gcd(b, a % b);
}
int check_prime(int a) {
  int c;
  for (c = 2; c <= a - 1; c++) {
    if (a % c == 0) return 0;
  }
  return 1;
}
string print24(string str) {
  string s = "";
  int h1 = (int)str[1] - '0';
  int h2 = (int)str[0] - '0';
  int hh = (h2 * 10 + h1 % 10);
  if (str[6] == 'A') {
    if (hh == 12) {
      s += "00";
      for (int i = 3; i <= 4; i++) s += str[i];
    } else {
      for (int i = 3; i <= 4; i++) s += str[i];
    }
  } else {
    if (hh == 12) {
      s += "12";
      for (int i = 3; i <= 4; i++) s += str[i];
    } else {
      hh = hh + 12;
      s += hh;
      for (int i = 3; i <= 4; i++) s += str[i];
    }
  }
  return s;
}
bool isVowel(char x) {
  return (x == 'a' || x == 'e' || x == 'i' || x == 'o' || x == 'u');
}
int main() {
  c_p_c();
  long long n, k;
  cin >> n >> k;
  double a[n], b[n];
  double sum = 0;
  for (long long i = 0; i < n; i++) cin >> a[i] >> b[i];
  for (long long i = 1; i < n; i++) {
    sum += sqrt(pow((a[i] - a[i - 1]), 2) + pow((b[i] - b[i - 1]), 2));
  }
  cout << std::setprecision(10) << (sum / 50) * k;
  return 0;
}
