#include <bits/stdc++.h>
#define rep(i,l,r) for (int i = l; i < r; i++)
#define repr(i,r,l) for (int i = r; i >= l; i--)
#define pb push_back
#define X first
#define Y second
#define debug(x) cerr << #x << " : " << x << endl;
#define all(x) x.begin() , x.end()
using namespace std;
typedef pair<int,int> pll;
typedef long long ll;
constexpr int N = 3e5+10;
int d[N],pr[N][19],n,a,b;
void bfs(){
queue<int> q;
q.push(a);
d[a] = 0;
while (!q.empty()){
int v = q.front();
if (v == b) break;
q.pop();
rep(l,0,n){
rep(r,l,n){
int s = pr[v][r],pw = (1 << (r+1))-(1 << l);
if (l) s -= pr[v][l-1];
if (d[v-s] > d[v]+1){
d[v-s] = d[v]+1;
q.push(v-s);
}
if (d[v+pw-s] > d[v]+1){
d[v+pw-s] = d[v]+1;
q.push(v+pw-s);
}
if (d[v+pw-2*s] > d[v]+1){
d[v+pw-2*s] = d[v]+1;
q.push(v+pw-2*s);
}
}
}
}
}
int main(){
ios_base :: sync_with_stdio(0); cin.tie(0);
memset(d,63,sizeof d);
string s,t;
cin >> n >> s >> t;
rep(i,0,n){
if (s[i] == '1') a += (1 << i);
if (t[i] == '1') b += (1 << i);
}
int y = (1 << n);
rep(i,1,y){
rep(j,0,n){
if (!j){
if (i&1) pr[i][j] = 1;
continue;
}
if (i&(1 << j)) pr[i][j] = pr[i][j-1]+(1 << j);
else pr[i][j] = pr[i][j-1];
}
}
bfs();
cout << d[b];
}
