#include<bits/stdc++.h>
#ifdef LOCAL
#include "D:\debug.h"
#else
#define cebug(...) "Orz_chUoNgnn_khanhtb"
#endif
using namespace std;
#define int long long
#define fi first
#define se second
#define pb push_back
#define ll long long
#define ii pair<int, int>
#define vi vector<int>
#define vll vector<ll>
#define vii vector<ii>
#define cd complex<double>
const ll mod = 1e9 + 7;
const ll INF = 1e18L + 5;
const double PI = acos(-1);
const int block = 320;
const int N = 1e6;
int tc, tt = 1;
int n;
string a, b;
int dp[N + 5][4][2];
bool ck(int i, int t) {
if(a[i] == b[i] && t == 0) return true;
if(b[i] == '0' && t == 1) return true;
if(b[i] == '1' && t == 2) return true;
if(a[i] != b[i] && t == 3) return true;
return false;
}
void solve() {
cin>>n>>a>>b;
for(int i=0; i<=n; i++)
for(int j=0; j<4; j++)
for(int k=0; k<2; k++)
dp[i][j][k] = INF;
a = ']' + a;
b = '[' + b;
dp[0][0][0] = 0;
for(int i=1; i<=n; i++)
for(int j=0; j<4; j++)
for(int k=0; k<2; k++)
if((k == 0 && ck(i, j)) || (k == 1 && !ck(i, j))){
dp[i][j][k] = dp[i - 1][j][k];
dp[i][j][k] = min(dp[i][j][k], dp[i - 1][j][1 ^ k] + 1);
for(int h=0; h<4; h++)
if(h != j) {
dp[i][j][k] = min(dp[i][j][k], dp[i - 1][h][k] + (j != 0));
dp[i][j][k] = min(dp[i][j][k], dp[i - 1][h][1 ^ k] + 1);
}
}
int ans = INF;
for(int i=0; i<4; i++) {
ans = min(ans, dp[n][i][0]);
ans = min(ans, dp[n][i][1] + 1);
}
cout<<ans;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
// freopen(".INP", "r", stdin);
// freopen(".OUT", "w", stdout);
for(int tc=1; tc<=tt; tc++) solve();
cerr<<"\nTime elapsed: "<<1000.0*clock()/CLOCKS_PER_SEC<<" ms.\n";
return 0;
}
