#include <bits/stdc++.h>

#define forn(i, n) for (int i = 0; i < int(n); i++)
#define nfor(i, n) for (int i = int(n) - 1; i >= 0; i--)
#define fore(i, l, r) for (int i = int(l); i < int(r); i++)
#define correct(x, y, n, m) (0 <= (x) && (x) < (n) && 0 <= (y) && (y) < (m))
#define all(a) (a).begin(), (a).end()
#define sz(a) int((a).size())
#define pb(a) push_back(a)
#define mp(x, y) make_pair((x), (y))
#define x first
#define y second

using namespace std;

typedef long long li;
typedef long double ld;
typedef pair<int, int> pt;

template<typename X> inline X abs(const X& a) { return a < 0? -a: a; }
template<typename X> inline X sqr(const X& a) { return a * a; }

template<typename A, typename B> inline ostream& operator<< (ostream& out, const pair<A, B>& p) { return out << "(" << p.x << ", " << p.y << ")"; }
template<typename T> inline ostream& operator<< (ostream& out, const vector<T>& a) { out << "["; forn(i, sz(a)) { if (i) out << ','; out << ' ' << a[i]; } return out << " ]"; }
template<typename T> inline ostream& operator<< (ostream& out, const set<T>& a) { return out << vector<T>(all(a)); }

inline ld gett() { return clock() / ld(CLOCKS_PER_SEC); }

const int INF = int(1e9);
const li INF64 = li(1e18);
const ld EPS = 1e-9, PI = 3.1415926535897932384626433832795;

const int N = 44;

int n, p;
array<string, N> a;

inline bool read() {
    if (!(cin >> n >> p)) return false;
    forn(i, n) assert(cin >> a[i]);
    return true;
}

inline void solve() {
    reverse(a.begin(), a.begin() + n);
    li ans = 0, k = 0;
    forn(i, n) {
        k *= 2;
        if (a[i] == "halfplus") k++;
        ans += k * p / 2;
    }
    cerr << "cnt=" << k << endl;
    cout << ans << endl;
}

int main() {
#ifdef SU1
    assert(freopen("input.txt", "rt", stdin));
    //assert(freopen("output.txt", "wt", stdout));
#endif

    cout << setprecision(10) << fixed;
    cerr << setprecision(5) << fixed;

    while (read()) {
        ld stime = gett();
        solve();
        cerr << "Time: " << gett() - stime << endl;
        //break;
    }

    return 0;
}