#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define REP(i,m,n) for(int i=(int)(m); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define RREP(i,m,n) for(int i=(int)(m); i>=(int)(n); i--)
#define rrep(i,n) RREP(i,n-1,0)
#define all(v) v.begin(), v.end()
const int inf = 1e9+7;
const ll longinf = 1LL<<60;
const ll mod = 1e9+7;

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int N;
  string s, t;
  cin >> N >> s >> t;
  for(int l=N; l<=2*N; l++) {
    string S(l, ' ');
    rep(i, N) S[i] = s[i];
    bool ok = true;
    rep(i, N) if(S[l-N+i] != ' ' && S[l-N+i] != t[i]) ok = false;
    if(ok) {
      cout << l << "\n";
      return 0;
    }
  }
  return 0;
}

#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; i++)
#define rrep(i, n) for (int i = n - 1; i >= 0; i--)
using namespace std;
#define INF ((1<<30)-1)
#define LINF (1LL<<60)
#define EPS (1e-10)
typedef long long ll;
typedef pair<ll, ll> P;
const int MOD = 1000000007;
const int MOD2 = 998244353;


int main(){
    int n;
    cin >> n;
    string s, t;
    cin >> s >> t;

    rep(i, n){
        if (s.substr(i) == t.substr(0,n-i)) {
            // cout << s << t.substr(n-i) << endl;
            cout << s.size() + t.substr(n-i).size() << endl;
            return 0;
        }
    }
    cout << 2 * n << endl;
    return 0;
}
