# include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 5;
int n, dp[N][2], pref[N][2];
unordered_set <char> st;
string a, b;
inline int calc (int l, int r, int type){
if (type == 0)
return pref[r][0] - pref[l - 1][0] + (b[l - 1] == b[l] && b[l] == '0');
return pref[r][1] - pref[l - 1][1] + (b[l - 1] == b[l] && b[l] == '1');
}
main(){
memset( dp, 0x3f3f3f3f, sizeof(dp) );
cin >> n >> a >> b;
a = ' ' + a;
b = ' ' + b;
for (int i = 1; i <= n; i++){
st.insert(a[i]);
if (b[i] != b[i - 1])
pref[i][ b[i] - 48 ] = 1;
pref[i][0] += pref[i - 1][0];
pref[i][1] += pref[i - 1][1];
}
if (st.size() == 1 && a[1] == '0'){
cout << calc(1, n, 1) << endl;
return 0;
}
dp[0][0] = 0;
for (int i = 1; i <= n; i++){
if (a[i] == b[i])
dp[i][0] = min( dp[i - 1][1], dp[i - 1][0] );
if (a[i] != b[i])
dp[i][1] = min( dp[i - 1][1], dp[i - 1][0] + 1);
for (int j = i; j >= 1; j--){
dp[i][0] = min( dp[i][0], dp[j - 1][0] + calc( j, i, 1 ) + 1 );
dp[i][0] = min( dp[i][0], dp[j - 1][0] + calc( j, i, 0 ) + 1 );
dp[i][0] = min( dp[i][0], dp[j - 1][1] + calc( j, i, 1 ) - (b[j] == '1') + 1 );
dp[i][0] = min( dp[i][0], dp[j - 1][1] + calc( j, i, 0 ) - (b[j] == '0') + 1 );
dp[i][1] = min( dp[i][1], dp[j - 1][1] + calc( j, i, 0 ) + 1 );
dp[i][1] = min( dp[i][1], dp[j - 1][0] + calc( j, i, 0 ) - (b[i] == '0') + 2 );
dp[i][1] = min( dp[i][1], dp[j - 1][1] + max(0, calc( j, i, 0 ) - (b[j] == '0') - (b[i] == '0') ) + 2 );
dp[i][1] = min( dp[i][1], dp[j - 1][1] + calc( j, i, 1 ) + 1 );
dp[i][1] = min( dp[i][1], dp[j - 1][0] + calc( j, i, 1 ) - (b[i] == '1') + 2 );
dp[i][1] = min( dp[i][1], dp[j - 1][1] + max(0, calc( j, i, 1 ) - (b[j] == '1') - (b[i] == '1') ) + 2 );
}
}
cout << min(dp[n][0], dp[n][1]) << endl;
}
/**
13
0101100101001
1011111000000
13
0001101001101
0101100011011
**/
