#include <bits/stdc++.h>
typedef long long ll;
using namespace std;
int dist[1<<18];
bool visited[1<<18];
void convert(string &x, int &X){
for (int i=0;i<(int)x.size();i++) if (x[i]=='1') X += (1<<i);
}
int main(){
cin.tie(NULL);
ios_base::sync_with_stdio(false);
int n;
string x, y;
cin >> n >> x >> y;
int X = 0, Y = 0;
convert(x, X); convert(y, Y);
queue<int> q;
q.push(X);
visited[X] = 1;
fill(dist, dist+(1<<18), 1e9);
dist[X] = 0;
int MX = (1<<n)-1;
while(!q.empty()){
int cur = q.front(); q.pop();
for (int i=0;i<n;i++){
int tmp = 0;
for (int j=i;j<n;j++){
tmp |= (1<<j);
if (!visited[cur|tmp]){
visited[cur|tmp] = 1;
q.push(cur|tmp);
dist[cur|tmp] = dist[cur]+1;
}
if (!visited[cur^tmp]){
visited[cur^tmp] = 1;
q.push(cur^tmp);
dist[cur^tmp] = dist[cur]+1;
}
if (!visited[cur&(MX^tmp)]){
visited[cur&(MX^tmp)] = 1;
q.push(cur&(MX^tmp));
dist[cur&(MX^tmp)] = dist[cur]+1;
}
}
}
}
cout << dist[Y];
return 0;
}
