#include <bits/stdc++.h>
using namespace std;
const int Nmax = 1e6 + 5;
int a[Nmax], b[Nmax], a0[Nmax], b0[Nmax], ones[Nmax], dp[Nmax];
int i, j, n;
int nr_ones(int x, int y)
{
return ones[y] - ones[x-1];
}
int main()
{
// freopen("input", "r", stdin);
cin.sync_with_stdio(false);
cin >> n;
string A, B;
cin >> A >> B;
for(i=1; i<=n; ++i)
a0[i] = A[i-1] - '0', b0[i] = B[i-1] - '0';
for(i=1; i<=n+1; ++i)
a[i] = a0[i-1] ^ a0[i], b[i] = b0[i-1] ^ b0[i];
for(i=1; i<=n+1; ++i) ones[i] = ones[i-1] + b[i];
for(i=1; i<=n+1; ++i)
{
dp[i] = dp[i-1] + (a[i] ^ b[i]);
for(j=1; j<i; ++j) /// flip cu schimbare j...i
dp[i] = min(dp[i], dp[j-1] + 2 + (a[i] ^ b[i] ^ 1) + (a[j] ^ b[j] ^ 1) + nr_ones(j+1, i-1) );
}
cout << (dp[n+1] + 1)/2 << '\n';
return 0;
}
