#include<iostream>
#include<cstdio>
#include<cmath>
#include<cassert>
#include<climits>
#include<algorithm>
#include<cstring>
using namespace std;
int main()
{
	freopen("racing.in","r",stdin);
	freopen("racing.out","w",stdout);
        int time,lu,s,x,p;
        cin>>time>>lu>>s>>p>>x;
        char q[1000010];
        for(int i=1;i<=lu;++i)
        {
                cin>>q[i];
        }
        int t=0,f=0;
        for(int i=1;i<=lu;++i)
        {
                if(t==time)
                {
                        cout<<f<<endl;
                        return 0;
                }
                if(t>time)
                {
                        cout<<f-1<<endl;
                        return 0;
                }
                if(q[i]=='u'||q[i]=='d')
                {
                        t=t+s+x;
                        f++;
                }
                if(q[i]=='f')
                {
                        t=t+p+p;
                        f++;
                }
        }
        cout<<lu<<endl;
        return 0;
}