#include <bits/stdc++.h>
using namespace std;
long long p, ans, num;
int n;
string s[500000];
int main() {
  cin >> n >> p;
  p /= 2;
  for (int i = 1; i <= n; ++i) {
    cin >> s[i];
  }
  for (int i = n; i >= 1; --i) {
    num *= 2;
    if (s[i] == "halfplus") num++;
    ans += num;
  }
  cout << ans * p << endl;
}
