/*raghav0307 - Raghav Gupta*/
#include <bits/stdc++.h>
using namespace std;
#define ff first
#define ss second
#define pb push_back
#define fast_io() ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
typedef long long ll;
#define int ll
const int MAX_SIZE = 1e6 + 5;
const int inf = 1e15;
int n;
string p, q;
int memo[MAX_SIZE][4];
int dp(int x, int y){
if(x == -1){
if(y == 0) return 0;
return 1;
}
if(memo[x][y] != -1) return memo[x][y];
int last_min = min(min(dp(x-1, 0), dp(x-1, 1) ), min(dp(x-1, 2), dp(x-1, 3)));
if(y == 0){
if(p[x] != q[x]) return memo[x][y] = inf;
return memo[x][y] = last_min;
}
if(y == 1){
if(q[x] != '0') return memo[x][y] = min(dp(x-1, y) + ( (x == 0 or q[x-1] == '0') ? 1 : 0), last_min + 2);
return memo[x][y]= min(dp(x-1, y), last_min + 1);
}
if(y == 2){
if(q[x] != '1') return memo[x][y] = min(dp(x-1, y) + ( (x == 0 or q[x-1] == '1') ? 1 : 0), last_min + 2);
return memo[x][y] = min(dp(x-1, y), last_min + 1);
}
if(y == 3){
if(q[x] == p[x]) return memo[x][y] = min(dp(x-1, y) + ( x == 0 or q[x-1] != p[x-1] ? 1 : 0), last_min + 2);
return memo[x][y] = min(dp(x-1, y), last_min + 1);
}
}
signed main(){
fast_io();
cin >> n >> p >> q;
memset(memo, -1, sizeof(memo));
int ans = min(min(dp(n-1, 0), dp(n-1, 1)), min(dp(n-1,2), dp(n-1,3)));
cout << ans << "\n";
// for(int i = 0; i < n; i++){
// for(int j = 0; j < 4; j++){
// cout << memo[i][j] << " ";
// }cout << "\n";
// }
return 0;
}
