#include <bits/stdc++.h>
using namespace std;

#define ll long long

void solve() {
	int n, a;
	string s;
	cin >> n >> a >> s;
	for (int i = 0; i < n; i++) {
		if (s[i] == 'x') {
			if (a > 0) {
				a--;
			}
		} else {
			a++;
		}
	}
	cout << a << "\n";
}

int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);

	int t = 1, i = 1;
	//cin >> t;
	while(t--) {
		//cout << "Case #" << i << ": ";
		solve();
		//i++;
	}
	return 0;
}


#include<bits/stdc++.h>

#define rep(i, n) for(int i=0;i<n;++i)
using namespace std;
typedef long long ll;

int main() {
    int n;
    double d, h;
    cin >> n >> d >> h;

    double max_h = 0;
    rep(i, n) {
        double x, y;
        cin >> x >> y;
        max_h = max(max_h, (d * y - h * x) / (d - x));
    }
    cout << setprecision(10) << max_h << endl;
}
