#include <bits/stdc++.h>
using namespace std;
auto minl(int &a, int b){
a = min(a, b);
}
const int MAX = 1e6 + 5;
const int inf = 1e9;
int n, dp[MAX][3];
// 0 : off
// 1 : on
// 2 : non
string a, b;
void process(){
cin >> n;
cin >> a >> b;
a = ' ' + a, b = ' ' + b;
dp[0][0] = inf, dp[0][1] = inf, dp[0][2] = 0;
for (int i = 1; i <= n; ++ i){
int tar = b[i] - '0';
for (int j : {0, 1, 2}) dp[i][j] = inf;
for (int j : {0, 1, 2}) if (dp[i - 1][j] != inf){
int tmp = dp[i - 1][j];
int tog = 0;
if (i > 1){
int las = j;
if (j > 1) las = a[i - 1] - '0';
int g = b[i - 1] - '0';
tog = (las != g);
}
for (int k : {0, 1, 2}){
if (k != j && max(k, j) < 2) continue;
int cur = k;
if (cur > 1) cur = a[i] - '0';
minl(dp[i][k], tmp + (k < 2 && j == 2) + (!tog && cur != tar));
}
}
//cout << dp[i][0] << ' ' << dp[i][1] << ' ' << dp[i][2] << endl;
}
cout << min({dp[n][0], dp[n][1], dp[n][2]});
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
process();
return 0;
}
