#include <bits/stdc++.h>
using namespace std;
int n, cnt = 1, ans = 1;
string s;
int main()
{
	cin >> n >> s;
	for (int i = 1;i < n;i++)
	{
		if (s[i] - s[i - 1] == 1)
		{
			cnt++;
		}
		else
		{
			ans = max (ans, cnt);
			cnt = 1;
		}
	}
	cout << ans;
	return 0;
}