#include <bits/stdc++.h>
using namespace std;
int n;
string a, b;
int dp[2100][2100] = {0};
int main() {
ios_base::sync_with_stdio(false); cin.tie(0);
cin >> n >> a >> b;
for (char &c : a) c -= '0';
for (char &c : b) c -= '0';
a = "$"+a, b = "$"+b;
memset(dp, 63, sizeof(dp));
dp[0][0] = 0;
for (int i = 1; i <= n; i++) {
for (int j = 0; j <= n; j++) {
if (a[i] != b[i]) {
if (j & 1) dp[i][j] = min(dp[i][j], dp[i-1][j]);
dp[i][j+1] = min(dp[i][j+1], dp[i-1][j]+1);
if (j > 0) dp[i][j-1] = min(dp[i][j-1], dp[i-1][j]);
}
if (a[i] == b[i]) {
if (j % 2 == 0) dp[i][j] = min(dp[i][j], dp[i-1][j]);
dp[i][j+1] = min(dp[i][j+1], dp[i-1][j]+1);
if (j > 0) dp[i][j-1] = min(dp[i][j-1], dp[i-1][j]);
}
if (b[i] == 0) {
for (int k = i; k <= n and b[k] == 0; k++) dp[k][j] = min(dp[k][j], dp[i-1][j]+1);
}
if (b[i] == 1) {
for (int k = i; k <= n and b[k] == 1; k++) dp[k][j] = min(dp[k][j], dp[i-1][j]+1);
}
}
}
int ans = INT_MAX;
for (int i = 0; i <= n; i++) ans = min(ans, dp[n][i]);
cout << ans << '\n';
}
