#include <bits/stdc++.h>
using namespace std;
const int nmax = 1e6;
const int inf = 1e9;
int dp[nmax+5][4];
// 0 nimic
// 1 off
// 2 on
// 3 toggle
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
int n; string a, b; cin >> n >> a >> b;
a = " " + a; b = " " + b;
for(int i=0; i<=n; i++)
for(int j=0; j<=3; j++)
dp[i][j] = inf;
dp[0][0] = 0;
for(int i=1; i<=n; i++) {
if(a[i] == '0' and b[i] == '0') {
dp[i][0] = min({dp[i-1][0], dp[i-1][1], dp[i-1][2], dp[i-1][3]});
dp[i][1] = min({dp[i-1][0] + 1, dp[i-1][1], dp[i-1][2] + 1, dp[i-1][3] + 1});
}
else if(a[i] == '0' and b[i] == '1') {
dp[i][2] = min({dp[i-1][0] + 1, dp[i-1][1] + 1, dp[i-1][2], dp[i-1][3] + 1});
dp[i][3] = min({dp[i-1][0] + 1, dp[i-1][1] + 1, dp[i-1][2] + 1, dp[i-1][3]});
}
else if(a[i] == '1' and b[i] == '0') {
dp[i][1] = min({dp[i-1][0] + 1, dp[i-1][1], dp[i-1][2] + 1, dp[i-1][3] + 1});
dp[i][3] = min({dp[i-1][0] + 1, dp[i-1][1] + 1, dp[i-1][2] + 1, dp[i-1][3]});
}
else if(a[i] == '1' and b[i] == '1') {
dp[i][0] = min({dp[i-1][0], dp[i-1][1], dp[i-1][2], dp[i-1][3]});
dp[i][2] = min({dp[i-1][0] + 1, dp[i-1][1] + 1, dp[i-1][2], dp[i-1][3] + 1});
}
}
cout << min({dp[n][0], dp[n][1], dp[n][2], dp[n][3]});
return 0;
}
