#include <cstdio>
#include <climits>
#include <iostream>

#include <vector>
#include <map>

#include <algorithm>

using namespace std;
typedef long long ll;

int n;
ll a, b;
ll T;

vector<bool> vOr;

vector<ll> pref;
vector<ll> suf;

ll getAns(int l, int r){
    ll ar = 0;
    if(r == 0 || l < 0) ar = 0;
    else ar = min((l+1)*a,r*a);
    return (l >= 0 ? suf[l]: 0) + pref[r] + ar;
}

int32_t main(){
    cin >> n >> a >> b >> T;

    vOr.resize(n);
    pref.resize(n);
    suf.resize(n);

    char c;
    for(int i = 0; i < n; i++){
        cin >> c;
        vOr[i] = (c=='w');
    }

    for(int i = 0; i < n; i++){
        pref[i] = (i > 0 ? a: 0) + (vOr[i] ? b: 0) + 1;
        if(i) pref[i] += pref[i-1];
    }

    ll lv = 0;
    for(int i = n-1; i >= 0; i--){
        suf[n-1-i] = a + (vOr[i] ? b: 0) + 1 + lv;
        lv = suf[n-1-i];
    }

    int ans = 0;
    int lp = n-1;
    for(int rp = 0; rp < n; rp++){
        while(getAns(lp,rp) > T && lp >= 0){
            lp--;
        }
        if(getAns(lp,rp) <= T)ans = max(ans, max(0,lp+1)+rp+1);
    }
    cout << min(ans,n) << endl;
}