#include <bits/stdc++.h>
using namespace std;
int main() {
  string q[41];
  long long n, p, i, count = 1, check = 1;
  cin >> n >> p;
  for (i = 0; i < n; i++) cin >> q[i];
  for (i = n - 2; i >= 0; i--) {
    if (q[i] == "halfplus") {
      count = count * 2 + 1;
      check++;
    } else
      count = count * 2;
  }
  cout << p * count - (p / 2) * check << endl;
  return 0;
}
