#include <bits/stdc++.h>
using namespace std;
int n;
string a, b;
int dp[2100][2][2] = {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] = 0;
for (int i = 1; i <= n; i++) {
if (a[i] == b[i]) {
int z = min(dp[i-1][1][0], dp[i-1][0][0]);
z = min(z, min(dp[i-1][1][1], dp[i-1][0][1]));
dp[i][0][0] = min(dp[i][0][0], z);
}
if (b[i] == 0) {
for (int j = i; j <= n and b[j] == 0; j++) dp[j][1][0] = min(dp[j][1][0], min(dp[i-1][0][0], dp[i-1][1][0]) + 1 );
for (int j = i; j <= n and b[j] == 0; j++) dp[j][1][1] = min(dp[j][1][1], min(dp[i-1][0][1], dp[i-1][1][1]) + 1 );
}
if (b[i] == 1) {
for (int j = i; j <= n and b[j] == 1; j++) dp[j][1][0] = min(dp[j][1][0], min(dp[i-1][0][0], dp[i-1][1][0]) + 1 );
for (int j = i; j <= n and b[j] == 1; j++) dp[j][1][1] = min(dp[j][1][1], min(dp[i-1][0][1], dp[i-1][1][1]) + 1 );
}
if (a[i] != b[i]) {
for (int j = i; j <= n and b[j] != a[j]; j++) dp[j][1][1] = min(dp[j][1][1], min(dp[i-1][1][1], dp[i-1][1][0]+1));
for (int j = i; j <= n and b[j] != a[j]; j++) dp[j][1][1] = min(dp[j][1][1], dp[i-1][0][0]+1);
}
}
int ans = INT_MAX;
for (int i = 0; i < 2; i++) for (int j = 0; j < 2; j++) ans = min(ans, dp[n][i][j]);
cout << ans << '\n';
}
