#include <bits/stdc++.h>
using namespace std;
int n;
string a, b;
int dp[2100][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;
for (int i = 1; i <= n; i++) {
if (a[i] == b[i]) {
int z = min(dp[i-1][1], dp[i-1][0]);
dp[i][0] = min(dp[i][0], z);
}
if (b[i] == 0) {
for (int j = i; j <= n and b[j] == 0; j++) dp[j][0] = min(dp[j][0], min(dp[i-1][0], dp[i-1][0]) + 1 );
for (int j = i; j <= n and b[j] == 0; j++) dp[j][1] = min(dp[j][1], min(dp[i-1][1], dp[i-1][1]) + 1 );
}
if (b[i] == 1) {
for (int j = i; j <= n and b[j] == 1; j++) dp[j][0] = min(dp[j][0], min(dp[i-1][0], dp[i-1][0]) + 1 );
for (int j = i; j <= n and b[j] == 1; j++) dp[j][1] = min(dp[j][1], min(dp[i-1][1], dp[i-1][1]) + 1 );
}
if (a[i] != b[i]) {
for (int j = i; j <= n and b[j] != a[j]; j++) dp[j][1] = min(dp[j][1], min(dp[i-1][1], dp[i-1][0]+1));
}
}
int ans = min(dp[n][0], dp[n][1]);
cout << ans << '\n';
}
/*
5
01100
11001
01100
11110
11001
*/
