#include "bits/stdc++.h"
using namespace std;
#define fi first
#define se second
#define ll long long
#define dbg(v) cerr<<#v<<" = "<<v<<'\n'
#define vi vector<int>
#define vl vector <ll>
#define pii pair<int,int>
#define vii vector < pii >
#define mp make_pair
#define db long double
#define pb push_back
#define all(s) s.begin(),s.end()
template < class P , class Q > ostream& operator<<(ostream& stream, pair < P , Q > v){ stream << "(" << v.fi << ',' << v.se << ")"; return stream;}
template < class T > ostream& operator<<(ostream& stream, const vector<T> v){ stream << "[ "; for (int i=0; i<(int)v.size(); i++) stream << v[i] << " "; stream << "]"; return stream;}
template < class T > T smin(T &a,T b) {if (a > b) a = b;return a;}
template < class T > T smax(T &a,T b) {if (a < b) a = b;return a;}
const int N = 1e6 + 5;
const int oo = 1e9;
char A[N];
char B[N];
int dp[N][2];
int d1[N],d2[N];
int main(void) {
int n;
cin>>n;
cin>>(A+1)>>(B+1);
dp[0][0] = 0;
dp[0][1] = 1;
for (int i = 1;i <= n;++i)
dp[i][0] = dp[i][1] = oo;
for (int i = 1;i <= n;++i) {
d1[i] = B[i] == '1' ? d1[i - 1] : i;
d2[i] = B[i] == '0' ? d2[i - 1] : i;
}
for (int i = 1;i <= n;++i) {
smin(dp[i][0],min(dp[i - 1][0],dp[i - 1][1]) + (A[i] != B[i]));
smin(dp[i][1],min(dp[i - 1][0] + 1,dp[i - 1][1]) + (A[i] == B[i]));
int Ind = B[i] == '1' ? d1[i] - 1 : d2[i] - 1;
int NInd = B[i] == '1' ? d2[d1[i] - 1] : d1[d2[i] - 1];
smin(dp[i][0],min(dp[Ind][0],dp[Ind][1]) + 1);
smin(dp[i][1],min(dp[Ind][0] + 1,dp[Ind][1]) + 1);
if (NInd >= 0)
smin(dp[i][1],dp[NInd][0] + 2);
}
cout << min(dp[n][0],dp[n][1]) << '\n';
return 0;
}
