#include <bits/stdc++.h>
using namespace std;
void __print(int x) { cerr << x; }
void __print(long x) { cerr << x; }
void __print(long long x) { cerr << x; }
void __print(unsigned x) { cerr << x; }
void __print(unsigned long x) { cerr << x; }
void __print(unsigned long long x) { cerr << x; }
void __print(float x) { cerr << x; }
void __print(double x) { cerr << x; }
void __print(long double x) { cerr << x; }
void __print(char x) { cerr << '\'' << x << '\''; }
void __print(const char *x) { cerr << '\"' << x << '\"'; }
void __print(const string &x) { cerr << '\"' << x << '\"'; }
void __print(bool x) { cerr << (x ? "true" : "false"); }
template <typename T, typename V>
void __print(const pair<T, V> &x) {
  cerr << '{';
  __print(x.first);
  cerr << ',';
  __print(x.second);
  cerr << '}';
}
template <typename T>
void __print(const T &x) {
  int f = 0;
  cerr << '{';
  for (auto &i : x) cerr << (f++ ? "," : ""), __print(i);
  cerr << "}";
}
void _print() { cerr << "]\n"; }
template <typename T, typename... V>
void _print(T t, V... v) {
  __print(t);
  if (sizeof...(v)) cerr << ", ";
  _print(v...);
}
const int N = 3e5 + 5;
long long a[N];
int main() {
  ios_base ::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  vector<int> v;
  long long n, p;
  cin >> n >> p;
  for (int i = 0; i < n; i++) {
    string s;
    cin >> s;
    if (s == "half")
      v.push_back(0);
    else
      v.push_back(1);
  }
  reverse(v.begin(), v.end());
  long long ans = 0;
  long long apples = 0;
  for (int i = 0; i < n; i++) {
    apples *= 2;
    if (v[i] == 1) {
      apples++;
    }
  }
  reverse(v.begin(), v.end());
  for (int i = 0; i < n; i++) {
    long long half = apples / 2;
    ans += p * half;
    if (apples & 1) ans += (p / 2);
    apples /= 2;
  }
  cout << ans;
  return 0;
}
