#include <bits/stdc++.h>
#define fi first
#define se second
#define FOR(i, a, b) for (int i = a, _b = b; i <= _b; ++i)
#define FORD(i, a, b) for (int i = a, _b = b; i >= _b; --i)
#define FORLL(i, a, b) for (ll i = a, _b = b; i <= _b; ++i)
#define FORDLL(i, a, b) for (ll i = a, _b = b; i >= _b; --i)
#define all(x) x.begin(), x.end()
#define uni(x) sort(all(x)), x.erase(unique(all(x)), x.end())
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define dbg(...) debug(#__VA_ARGS__, __VA_ARGS__)
template<typename T>
void __prine_one(const char *&s, const T &x)
{
while (*s == ' ') ++s;
const char *p = s;
int bal = 0;
while (*s)
{
if (*s == '(') ++bal;
else if (*s == ')') --bal;
else if (*s == ',' && bal == 0) break;
++s;
}
cerr.write(p, s - p) << " = " << x;
if (*s == ',')
{
cerr << " , ";
++s;
}
}
template<typename... Args>
void debug(const char *s, Args... args)
{
cerr << "[ ";
int dummy[] = {0, (__prine_one(s, args), 0)...};
(void)dummy;
cerr << " ]\n\n";
}
template<class X>
bool maximize(X &a, const X &b)
{
if (a < b)
{
a = b;
return true;
}
return false;
}
template<class X>
bool minimize(X &a, const X &b)
{
if (a > b)
{
a = b;
return true;
}
return false;
}
// --------------------------------------------------------------------------------------------
const int maxn = 1e6 + 3;
int n; vector<int> iState, fState;
// --------------------------------------------------------------------------------------------
namespace sub1
{
map<vector<int>, int> ID;
vector<vector<int>> states;
vector<int> D;
int tid = 0;
queue<int> q;
void Add(vector<int> &s, int dprev)
{
if (ID.count(s)) return;
ID[s] = ++tid;
D.push_back(dprev + 1);
states.push_back(s);
q.push(tid);
}
void solve()
{
ID[iState] = 0;
D.push_back(0);
states.push_back(iState);
q.push(0);
if (iState == fState) return cout << 0, void();
while (q.size())
{
int u = q.front(); q.pop();
// Type 1
{
FOR(i, 0, n - 1)
{
vector<int> nState = states[u];
FOR(j, i, n - 1)
{
nState[j] = 0;
Add(nState, D[u]);
if (nState == fState) return cout << D[tid], void();
}
}
}
// Type 2
{
FOR(i, 0, n - 1)
{
vector<int> nState = states[u];
FOR(j, i, n - 1)
{
nState[j] = 1;
Add(nState, D[u]);
if (nState == fState) return cout << D[tid], void();
}
}
}
// Type 3
{
FOR(i, 0, n - 1)
{
vector<int> nState = states[u];
FOR(j, i, n - 1)
{
nState[j] ^= 1;
Add(nState, D[u]);
if (nState == fState) return cout << D[tid], void();
}
}
}
}
}
}
namespace AC
{
void solve()
{
int res = 0;
FOR(i, 0, n - 1)
{
if (iState[i] == fState[i]) continue;
int j0 = i - 1, j1 = i - 1, jflip = i - 1, nxj0 = i - 1, nxj1 = i - 1;
int cur0 = 0, cur1 = 0, curflip = 0;
while (j0 + 1 < n && (fState[j0 + 1] == 0 || iState[j0 + 1] == 0))
{
++j0;
cur0 += iState[j0] != 0;
}
while (j1 + 1 < n && (fState[j1 + 1] == 1 || iState[j1 + 1] == 1))
{
++j1;
cur1 += iState[j1] != 1;
}
while (j0 + 1 < n && (fState[nxj0 + 1] == 0)) ++nxj0;
while (j1 + 1 < n && (fState[nxj1 + 1] == 1)) ++nxj1;
while (jflip + 1 < n && iState[jflip + 1] != fState[jflip + 1]) ++jflip, ++curflip;
int nxt = i - 1;
if (curflip >= cur0 && curflip >= cur1)
{
FOR(j, i, jflip)
iState[j] ^= 1;
nxt = jflip;
}
else if (cur0 >= curflip && cur0 >= cur1)
{
FOR(j, i, j0)
iState[j] = 0;
nxt = nxj0;
}
else
{
FOR(j, i, j1)
iState[j] = 1;
nxt = nxj1;
}
++res;
// dbg(i, cur0, cur1, curflip, nxt);
i = nxt;
}
cout << res;
}
}
void solve()
{
cin >> n;
FOR(i, 1, n)
{
char ch; cin >> ch;
iState.push_back(ch - '0');
}
FOR(i, 1, n)
{
char ch; cin >> ch;
fState.push_back(ch - '0');
}
// if (n <= 18) return sub1 :: solve(), void();
AC :: solve();
}
signed main()
{
ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define TASK "TEST"
if (fopen(TASK".INP", "r"))
{
freopen(TASK".INP", "r", stdin);
freopen(TASK".OUT", "w", stdout);
}
solve();
return 0;
}
