#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define rep(a, b) for(int a = 0; a < (b); ++a)
#define st first
#define nd second
#define pb push_back
#define all(a) a.begin(), a.end()
const int LIM=1e6+7, INF=1e9+7;
int dp[LIM][4][4];
int rob(int x, int k) {
if(k==0) return 0;
if(k==1) return 1;
if(k==2) return x^1;
return x;
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(0);
int n;
string s, t;
cin >> n >> s >> t;
rep(i, 4) rep(j, 4) dp[0][i][j]=INF;
dp[0][3][3]=0;
rep(i, n) {
rep(a, 4) rep(b, 4) dp[i+1][a][b]=INF;
rep(a, 4) rep(b, 4) {
if(a==3 && b!=3) continue;
dp[i+1][a][b]=min(dp[i+1][a][b], dp[i][a][b]);
dp[i+1][3][3]=min(dp[i+1][3][3], dp[i][a][b]);
dp[i+1][a][3]=min(dp[i+1][a][3], dp[i][a][b]);
dp[i+1][b][3]=min(dp[i+1][b][3], dp[i][a][b]);
rep(c, 3) {
dp[i+1][a][c]=min(dp[i+1][a][c], dp[i][a][b]+1);
dp[i+1][b][c]=min(dp[i+1][b][c], dp[i][a][b]+1);
dp[i+1][c][3]=min(dp[i+1][c][3], dp[i][a][b]+1);
rep(d, 3) dp[i+1][c][d]=min(dp[i+1][c][d], dp[i][a][b]+2);
}
}
rep(a, 4) rep(b, 4) {
if(a==3 && b!=3) {
dp[i+1][a][b]=INF;
continue;
}
int p=s[i]-'0';
p=rob(p, a);
p=rob(p, b);
if(p!=t[i]-'0') dp[i+1][a][b]=INF;
}
}
int ans=INF;
rep(a, 4) rep(b, 4) ans=min(ans, dp[n][a][b]);
cout << ans << '\n';
}
