#include <bits/stdc++.h>
//#pragma GCC optimize("Ofast")
#define fi first
#define se second
#define ll long long
#define dl double long
using namespace std;
const int NN = 4e3 + 7;
const int N = 1e6 + 7;
const int M = 22;
const int mod = 1e9 + 7;
const ll inf = 1e18 + 7;
const dl rf = 1e-14;
const int B = sqrt(N);
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int n;
int p1[N];
int p2[N];
int p3[N];
char a[N];
char b[N];
int d[N][3];
vector < pair < int , int > > bl;
int get( int l , int r )
{
int res = 0;
for( int i = 0; i < (int)bl.size(); i++ ){
auto x = bl[i];
if( x.fi >= l && x.fi <= r ){
res += 1;
if( i + 1 < (int)bl.size() ){
int j = i + 1;
int y;
if( b[x.se] == '0' )y = p1[bl[j].fi] - p1[bl[j - 1].se];
else y = p2[bl[j].fi] - p2[bl[j - 1].se];
while( j < (int)bl.size() && bl[j].fi >= l && bl[j].fi <= r && bl[j].fi - bl[j - 1].se ==
y && b[bl[j].fi] == b[x.se] ){
j += 1;
if( b[x.se] == '0' )y = p1[bl[j].fi] - p1[bl[j - 1].se];
else y = p2[bl[j].fi] - p2[bl[j - 1].se];
}
i = j - 1;
}
}
}
return res;
}
void solve1()
{
cin >> n;
for( int i = 1; i <= n; i++ ){
cin >> a[i];
}
for( int i = 1; i <= n; i++ ){
cin >> b[i];
}
for( int i = 1; i <= n; i++ ){
if( a[i] != b[i] )continue;
int j = i;
while( j <= n && a[j] == b[j] )j += 1;
bl.push_back({i , j - 1});
i = j - 1;
}
for( int i = 1; i < N; i++ ){
for( int j = 0; j < 3; j++ ){
d[i][j] = 1e9;
}
}
for( int i = 1; i <= n; i++ ){
p1[i] = p1[i - 1] + (b[i] == '0');
p2[i] = p2[i - 1] + (b[i] == '1');
p3[i] = p3[i - 1] + (b[i] == a[i]);
}
for( int i = 1; i <= n; i++ ){
if( a[i] == b[i] ){
for( int j = 0; j < 3; j++ ){
for( int h = 0; h < 3; h++ ){
d[i][j] = min( d[i][j] , d[i - 1][h] );
}
//cout << i << " " << j << " " << d[i][j] << "\n";
}
}else{
int l = 1 , r = i + 1;
while( l < r ){
int m = (l + r) / 2;
if( p1[i] - p1[m - 1] == i - m + 1 )r = m;
else l = m + 1;
}
vector < int > v;
v.push_back(l);
l = 1 , r = i + 1;
while( l < r ){
int m = (l + r) / 2;
if( p2[i] - p2[m - 1] == i - m + 1 )r = m;
else l = m + 1;
}
v.push_back(l);
l = 1 , r = i + 1;
while( l < r ){
int m = (l + r) / 2;
if( p3[i] - p3[m - 1] > 0 )l = m + 1;
else r = m;
}
v.push_back(l);
for( int j = 0; j < 3; j++ ){
if( v[j] == i + 1 )v[j] += 2;
for( int h = 0; h < 3; h++ ){
d[i][j] = min( d[i][j] , d[v[j] - 1][h] + 1 );
}
//cout << i << " " << j << " " << v[j] << " " << d[i][j] << "\n";
}
for( int j = i; j >= 1; j-- ){
int x = 1e9;
for( int h = 0; h < 3; h++ )x = min( x , d[j - 1][h] );
d[i][2] = min( d[i][2] , get( j , i ) + 1 + x );
}
}
}
cout << min({ d[n][0] , d[n][1] , d[n][2] });
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
//freopen( "input.txt" , "r" , stdin );
//freopen( "output.txt" , "w" , stdout );
int cghf = 1;//cin >> cghf;
while( cghf-- ){
solve1();
}
}
