#include<bits/stdc++.h>using namespace std;long long n,p,ans=0,total=0,apple=0;int main(){ string a[100000]; cin>>n>>p; p=p>>1; for(int i=1;i<=n;i++) { cin>>a[i];}for(int i=n;i>=1;i--){ total=total*2; if(a[i]=="halfplus") total++; apple+=total; } cout<<apple*p; return 0;}