Fork

#include<iostream>
#include<string.h>
using namespace std;
int main()
{
    int n;
    cin>>n;
    int t=1;
    string s;
    string f="fork";
    int sum=0;
    while(n--)
    {
        cin>>s;
        if(s==f)
            t=t*2%100000007;
        else
            sum=(sum+t)%100000007;
    }
    cout<<sum;
}