using namespace std;
using ll = long long;
using ii = pair<int, int>;
using vi = vector<ll>;
template <typename InputIterator,
typename T = typename iterator_traits<InputIterator>::value_type>
void read_n(InputIterator it, int n)
{
copy_n(istream_iterator<T>(cin), n, it);
}
template <typename InputIterator,
typename T = typename iterator_traits<InputIterator>::value_type>
void write(InputIterator first, InputIterator last, const char *delim = "\n")
{
copy(first, last, ostream_iterator<T>(cout, delim));
}
using predicate = function<bool(ll)>;
ll n, a, b, t;
string s;
vi rot;
ll bs(ll l, ll r, predicate p)
{
while (l < r)
{
ll m = l + (r - l) / 2;
if (p(m))
r = m;
else
l = m + 1;
}
if (not p(l))
return -1;
return l;
}
int main(void)
{
ios::sync_with_stdio(false), cin.tie(NULL);
cin >> n >> a >> b >> t;
cin >> s;
rot.resize(n);
transform(begin(s), end(s), begin(rot), [](char c) { return b * (c == 'w'); });
partial_sum(begin(rot), end(rot), begin(rot));
ll ans = 0;
for (ll i = 0; i < n; ++i)
{
ll solo = rot[i] + a * i + (i + 1);
if (solo > t)
break;
ans = max(ans, i + 1);
if (i < n - 1)
{
ll right = solo + a * i;
if (right > t)
continue;
auto left_cost = [](ll ix) -> ll {
return a * (n - ix) + (n - ix) + rot[n - 1] - rot[ix - 1];
};
auto ok = [right, left_cost](ll ix) {
return right + left_cost(ix) <= t;
};
ll j = bs(i + 1, n - 1, ok);
if (j == -1)
continue;
ans = max(ans, i + 1 + (n - j));
}
}
cout << ans << endl;
return 0;
}