//Challenge: Accepted
#include <iostream>
#include <algorithm>
#include <vector>
#include <utility>
#define ll long long
#define maxn 1000005
#define pii pair<int, int>
#define ff first
#define ss second
#define io ios_base::sync_with_stdio(0);cin.tie(0);
using namespace std;
string sa, sb;
int a[maxn], b[maxn], pref[maxn], diff[maxn], pdif[maxn];
int dp[maxn];
inline int seg(int l, int r) {
if (l > r) return 0;
return pref[r] - (l ? pref[l - 1] : 0);
}
int main() {
io
int n;
cin >> n;
cin >> sa >> sb;
sa += '0', sb += '0';
n++;
for (int i = 0;i < n;i++) {
a[i] = (sa[i] == '1') ^ (i ? (sa[i - 1] == '1') : 0);
b[i] = (sb[i] == '1') ^ (i ? (sb[i - 1] == '1') : 0);
diff[i] = a[i] ^ b[i];
pref[i] = (b[i] == 1 ? 1 : 0) + (i ? pref[i - 1] : 0);
pdif[i] = diff[i] + (i ? pdif[i - 1] : 0);
//cout << pref[i] << " " << pdif[i] << endl;
}
for (int i = 0;i < n;i++) {
dp[i] = pdif[i];
for (int j = 0;j < i - 1;j++) {
dp[i] = min(dp[i], dp[j] + 4 - (diff[j + 1] + diff[i]) + seg(j + 2, i - 1));
dp[i] = min(dp[i], dp[j] + pdif[i] - pdif[j]);
}
//cout << dp[i] << " ";
}
//cout << endl;
cout << (dp[n - 1] + 1) / 2 << "\n";
}
/*
8
11011100
01101001
13
1010010010100
0000111001011
18
001100010010000110
110110001000100101
*/
