#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

#define RREP(i,s,e) for (int i = e-1; i >= s; i--)
#define rrep(i,n) RREP(i,0,n)
#define REP(i,s,e) for (int i = s; i < e; i++)
#define rep(i,n) REP(i,0,n)

int main() {
    int d;
    string s,t;
    cin >> d;
    rep (i,d) s.push_back('x');
    cin >> t;
    s += t;
    cin >> t;
    s += t;
    rep (i,d) s.push_back('x');

    vector<int> a{0};
    char now = 'x';
    int cnt = 0;
    int ans = 0;
    rep (i,14+d*2) {
        if (s[i] == now)
            cnt++;
        else {
            a.push_back(cnt);
            cnt = 1;
            now = s[i];
        }
    }
    a.push_back(cnt);
    a.push_back(0);
    for (int i = 1; i < a.size()-1; i+=2) {
        if (a[i] > d)
            ans = max(ans, d + max(a[i-1],a[i+1]));
        else
            ans = max(ans, a[i-1] + a[i] + a[i+1]);
    }
    cout << ans << endl;
    return 0;
}