#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimization("unroll-loops")
using namespace std;
const long long MOD = 1e+9 + 7;
const long long INF = 0x7f7f7f7f7f7f7f7f;
const int INFi = 0x7f7f7f7f;
const long long MAXN = 1e+5 + 7;
vector<long long> adj[MAXN];
long long visit[MAXN] = {};
int dx8[] = {0, 1, 1, 1, 0, -1, -1, -1}, dy8[] = {1, 1, 0, -1, -1, -1, 0, 1};
int dx4[] = {0, 1, 0, -1}, dy4[] = {1, 0, -1, 0};
int t = 1;
long long n, p;
string second[100];
void MAIN() {
  cin >> n >> p;
  long long ans = 0;
  long long ans1 = 0;
  for (long long i = 0; i < n; i++) cin >> second[i];
  for (long long i = n - 1; i >= 0; i--) {
    if (second[i] == "half") {
      ans *= 2;
    } else {
      ans *= 2;
      ans++;
    }
  }
  for (long long i = 0; i < n; i++) {
    if (second[i] == "half") {
      ans1 += ans / 2 * p;
      ans /= 2;
    } else {
      ans1 += ans / 2 * p + p / 2;
      ans /= 2;
    }
  }
  cout << ans1 << endl;
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cout << fixed;
  cout << setprecision(10);
  ;
  mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
  ;
  while (t--) {
    MAIN();
  }
}
