#include <iostream>
#include <cstdio>
 
using namespace std;
 
long long M,T,U,F,D;
char lk[100001];
int sj[100001];
long long tot=0,tz;
 
void input();
 
int main()
{
	freopen("racing.in","r",stdin);
	freopen("racing.out","w",stdout);
	
	input();
	for(int i=0;i<T;i++)
	{
		if(lk[i]=='u') 
		{
			sj[i]=U+D;
		}
		if(lk[i]=='d') 
		{
			sj[i]=U+D;
		}
		if(lk[i]=='f') 
		{
			sj[i]=F*2;
		}
	}	
	for(int i=0;i<T;i++)
	{
		if(tot+sj[i]<=M)
		{
			tot+=sj[i];
		}
		else
		{
			tz=i;
			break;
		}
	}
	cout<<tz<<endl;
	fclose(stdin);
	fclose(stdout);
	return 0;
}
 
void input()
{
	cin>>M>>T>>U>>F>>D;
	for(int i=0;i<T;i++)
	{
		cin>>lk[i];	
	}
}