var time,n,u,d,f,i,num:longint;

x:char;

a:array[0..10000]of longint;

begin

read(time,n,u,f,d);

i:=0;

while num<time do

begin

inc(i); readln(x);

if x='f' then inc(num,f*2)

else inc(num,u+d);

if num>=time then writeln(i-1);

end;

end.