#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("O3,unroll-loops")
// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
// Ofast, O0, O1, O2, O3, unroll-loops, fast-math, trapv
typedef long long ll;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
#define Mp make_pair
#define sep ' '
#define endl '\n'
#define F first
#define S second
#define pb push_back
#define all(x) (x).begin(),(x).end()
#define kill(res) cout << res << '\n', exit(0);
#define set_dec(x) cout << fixed << setprecision(x);
#define fast_io ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define file_io freopen("input.txt", "r", stdin) ; freopen("output.txt", "w", stdout);
const ll N = 1e6 + 50;
const ll inf = 1e9 + 7;
ll n, dp[N][6];
string s, t;
int main(){
fast_io;
cin >> n >> s >> t;
s = "$" + s; t = "$" + t;
for(int i = 0; i <= n; i++) for(int j = 0; j < 6; j++) dp[i][j] = inf;
dp[0][0] = 0;
for(int i = 1; i <= n; i++){
if(t[i] == '0') dp[i][5] = min({dp[i-1][0] + 2, dp[i-1][1] + 1, dp[i-1][4] + 1, dp[i-1][5]});
if(t[i] == '1') dp[i][4] = min(dp[i-1][0] + 1, dp[i-1][4]);
dp[i][4] = min(dp[i][4], dp[i][5]);
// hame 0 with c
if(t[i] == '1') dp[i][3] = min({dp[i][0] + 2, dp[i-1][1] + 1, dp[i-1][2] + 1, dp[i-1][3]});
// hame 0 without
if(t[i] == '0') dp[i][2] = min(dp[i-1][0] + 1, dp[i-1][2]);
dp[i][2] = min({dp[i][2], dp[i][3]});
if(s[i] != t[i]) dp[i][1] = min(dp[i-1][1], dp[i-1][0] + 1);
dp[i][1] = min({dp[i][1], dp[i][3], dp[i][5]});
if(s[i] == t[i]) dp[i][0] = dp[i-1][0];
dp[i][0] = min({dp[i][0], dp[i][1], dp[i][2], dp[i][3], dp[i][4], dp[i][5]});
}
cout << dp[n][0];
}
