#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn = 1e6 + 10;
int dp[maxn][4][4][4];
int transform(int x, int query){
if (query == 0)
return x;
else if (query == 1)
return 0;
else if (query == 2)
return 1;
else
return 1 ^ x;
}
char transfer(char s, int fi, int se, int th){
int q = (int)(s - '0');
q = transform(q, fi);
q = transform(q, se);
q = transform(q, th);
return (char)(q + '0');
}
bool C(int x){
return x > 0;
}
int lcs[5][5];
int pd[5][5][5][5][5][5];
int cost(int fi, int se, int th, int Fi, int Se, int Th){
if (pd[fi][se][th][Fi][Se][Th] != -1)
return pd[fi][se][th][Fi][Se][Th];
vector<int> a = {fi, se, th};
vector<int> b = {Fi, Se, Th};
int cnt = C(Fi) + C(Se) + C(Th);
for (int i = 1; i <= 3; i++){
for (int j = 1; j <= 3; j++){
lcs[i][j] = max(lcs[i - 1][j], lcs[i][j - 1]);
if (a[i - 1] == 0 or b[i - 1] == 0)
continue;
lcs[i][j] = max(lcs[i][j], (lcs[i - 1][j - 1] + 1) * (a[i - 1] == b[j - 1]));
}
}
// cout << fi << " " << se << " " << th << " ----- " << cnt - lcs[3][3] << " -----> " << Fi << " " << Se << " " << Th << endl;
return pd[fi][se][th][Fi][Se][Th] = cnt - lcs[3][3];
}
int main(){
ios_base::sync_with_stdio(false);
memset(pd, -1, sizeof pd);
int n;
string s, t;
cin >> n >> s >> t;
memset(dp, 63, sizeof dp);
dp[0][0][0][0] = 0;
int answer = n;
for (int i = 1; i <= n; i++){
for (int j = 0; j <= 3; j++){
for (int k = max(0, j); k <= 3; k++){
for (int p = max(0, k); p <= 3; p++){
char nex = transfer(s[i - 1], j, k, p);
if (nex != t[i - 1])
continue;
for (int x = 0; x <= 3; x++){
for (int y = max(0, x); y <= 3; y++){
for (int z = max(0, y); z <= 3; z++){
dp[i][j][k][p] = min(dp[i][j][k][p], dp[i - 1][x][y][z] + cost(x, y, z, j, k, p));
}
}
}
if (i == n)
answer = min(answer, dp[i][j][k][p]);
}
}
}
}
cout << answer << endl;
}
