#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <fstream>
#include <algorithm>
#include <string>
using namespace std;
string a, b, vals[16] = {"", "2", "0", "1", "01", "02", "10", "12", "20", "21", "012", "021", "102", "120", "201", "210"};
int n, dp[16] = {0, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3} , sw[16], num[16] = {0, 0, 48, 49, 49, 49, 48, 48, 48, 49, 48, 49, 49, 48, 49, 48};
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL); cin >> n >> a >> b;
for (int i = 0; i < n; i++){
sw[0] = 1000000000; sw[1] = 1000000000;
if (a[i] == b[i]){
sw[0] = dp[0];
for (int j = 1; j < 16; j++){
sw[0] = min(sw[0], dp[j]);
}
} else {
sw[1] = dp[0]+1;
for (int j = 1; j < 16; j++){
int sub = 0;
for (char a : vals[j]){
if (a == '2'){
sub++; break;
}
}
sw[1] = min(sw[1], dp[j]+1-sub);
}
}
for (int j = 2; j < 16; j++){
if (num[j] == b[i]){
int vs = vals[j].size();
sw[j] = dp[0]+vs;
for (int k = 1; k < 16; k++){
int count = 0, num = 0, ns = vals[k].size();
for (char a : vals[j]){
for (int l = count; l < ns; l++){
if (vals[k][l] == a){
count = l+1; num++; break;
}
}
}
sw[j] = min(sw[j], dp[k]+vs-num);
}
} else {
sw[j] = 1000000000;
}
}
swap(sw, dp);
}
int ans = 1000000000;
for (int i = 0; i < 16; i++){
ans = min(ans, dp[i]);
}
cout << ans << endl;
}
