#include <cstdio>
#include <iostream>
#include <cmath>
#include <assert.h>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <cstring>
#include <algorithm>
#define sc scanf
#define pr printf
#define pb push_back
#define mp std::make_pair
#define fr first
#define se second

using namespace std;

typedef std::pair<int, int> pii;
typedef std::pair<double, double> pdd;

const int MN = 1000010;
const long long M = -(1LL << 50);
const long long MAX_LONG = std::numeric_limits<long long>::max();
const long long MIN_LONG = std::numeric_limits<long long>::min() + (1LL << 54);
const int MAX_INT = std::numeric_limits<int>::max();
const int MIN_INT = std::numeric_limits<int>::min();

long long l[MN], r[MN];
int n, a, b, T;
char s[MN];

int main() {
    //freopen("in.txt", "r", stdin); freopen("out.txt", "w", stdout);
    //freopen("path.in", "r", stdin); freopen("path.out", "w", stdout);

    sc("%d%d%d%d", &n, &a, &b, &T);
    sc(" %s", s);

    for (int i = n - 1; i > 0; i--) {
        l[n - i] = l[n - i - 1] + 1 + (s[i] == 'w') * 1LL * b;
    }

    for (int i = 1; i < n; i++) {
        r[i] = r[i - 1] + 1 + (s[i] == 'w') * 1LL * b;
    }
/*
    for (int i = 0; i < n; i++) {
        pr("%d %d\n", l[i], r[i]);
    }
*/
    int t = 1 + (s[0] == 'w') * b;
    if (t > T) {
        pr("0\n");
        return 0;
    }

    T -= t;
    int ans = 1;

    for (int k = 0; k < 2; k++) {
        int j = n - 1;
        for (int i = 0; i < n; i++) {
        /*
            pr("-> %d %d\n", l[i] + i * a, T);
*/
            if (1LL * l[i] + 1LL * i * a > 1LL * T) {
                break;
            }

            while (j > 0 && (1LL * l[i] + 1LL * (i + 1LL * i + j) * 1LL * a + r[j]) > 1LL * T) {
                //pr("%d %d\n", j, (l[i] + (i + i + j) * a + r[j]));
                j--;
            }
            ans = max(ans, i + j + 1);
        }
        swap(l, r);
    }

    pr("%d\n", min(n, ans));

    return 0;
}