#include<bits/stdc++.h>
using namespace std ;
typedef long long ll ;
#define MAXN 1000007
int n ;
string a , b ;
int dp[ MAXN ] ;
void input ( ) {
cin >> n >> a >> b ;
}
void solve ( ) {
int diff = 0 ;
int mn_alt = 3 * MAXN ;
for ( int i = 1 ; i <= n ; ++ i ) {
dp[ i ] = MAXN ;
if ( a[ i - 1 ] == b[ i - 1 ] ) {
dp[ i ] = min ( dp[ i ] , dp[ i - 1 ] ) ;
}
else {
dp[ i ] = min ( dp[ i ] , dp[ i - 1 ] + 1 ) ;
}
if ( i > 1 && b[ i - 1 ] != b[ i - 2 ] ) {
++ mn_alt ;
}
dp[ i ] = min ( dp[ i ] , ( mn_alt + 1 ) / 2 ) ;
if ( a[ i - 1 ] != b[ i - 1 ] ) { ++ diff ; }
else { diff = 0 ; }
if ( diff > 0 ) {
dp[ i ] = min ( dp[ i ] , dp[ i - diff ] + 1 ) ;
}
mn_alt = min ( mn_alt , 2 * dp[ i - 1 ] + 2 ) ;
}
cout << dp[ n ] << "\n" ;
}
int main ( ) {
//freopen ( "dictionary.in" , "r" , stdin ) ;
ios_base :: sync_with_stdio ( false ) ;
cin.tie ( NULL ) ;
int t = 1 ;
// cin >> t ;
while ( t -- ) {
input ( ) ;
solve ( ) ;
}
return 0 ;
}
