#include <bits/stdc++.h>
using namespace std;
#define ff first
#define ss second
#define pb push_back
typedef pair<int, int> pii;

signed main() {
    ios::sync_with_stdio(0), cin.tie(0);
    int k, Mxans = 0, ans = 0;
    vector<pii> v;
    string a;
    cin >> k >> ws >> a;
    v.pb({(isupper(a[0]) ? 1 : 0), 1});
    for(int i=1; i<a.size(); i++) {
        int x = (isupper(a[i]) ? 1 : 0);
        if(v.back().ff == x)
            v.back().ss++;
        else
            v.pb({x, 1});
    }
    for(int i=0; i<v.size(); i++) {
        if(v[i].ss == k || (v[i].ss > k && ans == 0)) {
            ans += k;
            Mxans = max(ans, Mxans);
        }
        else if(v[i].ss > k) {
            ans += k;
            Mxans = max(ans, Mxans);
            ans = k;
        }
        else {
            Mxans = max(ans, Mxans);
            ans = 0;
        }
    }
    cout << Mxans << '\n';
}