#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef pair <int,int> ii;
const int N = 2e3 + 5;
const int inf = 2e9;
const int SQ = 300;
int n,d[2][N][N],dp[N][2];
char a[2][N],b[N];
int f(int cur,int w) {
if (cur == n + 1)
return 0;
int &res = dp[cur][w];
if (res != -1)
return res;
res = 1e9;
for (int i = cur ; i <= n ; i++)
res = min(res,d[w][cur][i] + f(i + 1,!w));
return res += (w == 1);
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL) ; cout.tie(NULL);
cin >> n >> (a[0] + 1) >> (b + 1);
for (int i = 1 ; i <= n ; i++)
a[1][i] = !(a[0][i] - '0') + '0';
for (int w = 0 ; w < 2 ; w++) {
for (int i = n ; i >= 1 ; i--) {
int j = i;
while(j + 1 <= n && b[j + 1] == b[i])
j++;
int flag = 0;
for (int k = i ; k <= j ; k++) {
if (a[w][k] != b[k])
flag = 1;
d[w][i][k] = flag;
}
for (int k = j + 1 ; k <= n ; k++)
d[w][i][k] = d[w][i][j] + d[w][j + 1][k];
}
}
memset(dp,-1,sizeof dp);
cout << min(f(1,0),f(1,1)) << endl;
}
