#include <bits/stdc++.h>
#define rep(i,n) for(int i=0; i<(n); ++i)
#define repx(i,x,n) for(int i=x; i<(n); ++i)
#define fixed_setprecision(n) fixed << setprecision((n))
#define execution_time(ti) printf("Execution Time: %.4lf sec\n", 1.0 * (clock() - ti) / CLOCKS_PER_SEC);
#define pai 3.1415926535897932384
#define NUM_MAX 2e18
#define NUM_MIN -1e9
using namespace std;
using ll = long long;
using P = pair<int,int>;
template<class T> inline bool chmax(T& a, T b){ if(a<b){ a=b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b){ if(a>b){ a=b; return 1; } return 0; }
int main() {
int N;
string s, t;
cin >> N >> s >> t;
int copy=0, len=N;
for(int i=0; i<N; i++){
int ok = 1;
for(int j=0; j<N; j++){
if(i+j<N) if(s[i+j] != t[j]) ok = 0;
}
if(ok) len = min(len, i);
}
string ans = s.substr(0, len) + t;
cout << ans.size() << endl;
return 0;
}