#include <bits/stdc++.h>
//#define int long long
//#pragma GCC optimize("Ofast")
//#pragma comment(linker, "/stack:200000000")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4")
#define file(s) freopen(s".in","r",stdin); freopen(s".out","w",stdout);
#define forev(i, b, a) for(int i = (b); i >= (a); --i)
#define forn(i, a, b) for(int i = (a); i <= (b); ++i)
#define all(x) x.begin(), x.end()
#define sz(s) (int)s.size()
#define pb push_back
#define ppb pop_back
#define mp make_pair
#define s second
#define f first
using namespace std;
typedef pair < long long, long long > pll;
typedef pair < int, int > pii;
typedef unsigned long long ull;
typedef vector < pii > vpii;
typedef vector < int > vi;
typedef long double ldb;
typedef long long ll;
typedef double db;
const int inf = 1e9, maxn = 4e5 + 148, mod = 1e9 + 7, N = 1e6 + 11;
const int dx[] = {1, -1, 0, 0}, dy[] = {0, 0, 1, -1}, block = 333;
const pii base = mp(1171, 3307), Mod = mp(1e9 + 7, 1e9 + 9);
const db eps = 1e-12, pi = 3.14159265359;
const ll INF = 1e18;
int n, dp[N][2], prv[N], T[N << 2][2];
char s[N], t[N];
void update (int pos, int lvl, int x, int v = 1, int tl = 0, int tr = n) {
if (tl == tr) {
T[v][lvl] = x;
return;
}
int tm = (tl + tr) >> 1;
if (pos <= tm)
update(pos, lvl, x, v << 1, tl, tm);
else
update(pos, lvl, x, v << 1 | 1, tm + 1, tr);
T[v][lvl] = min(T[v << 1][lvl], T[v << 1 | 1][lvl]);
}
int get (int l, int r, int lvl, int v = 1, int tl = 0, int tr = n) {
if (l > r || tl > r || l > tr)
return inf;
if (l <= tl && tr <= r)
return T[v][lvl];
int tm = (tl + tr) >> 1;
return min(get(l, r, lvl, v << 1, tl, tm), get(l, r, lvl, v << 1 | 1, tm + 1, tr));
}
main () {
scanf("%d\n%s\n%s", &n, s + 1, t + 1);
for (int i = 1; i <= n; ++i) {
prv[i] = i - 1;
if (i > 1 && t[i] == t[i - 1])
prv[i] = prv[i - 1];
}
dp[0][1] = inf;
update(0, 1, inf);
int lst = 0;
for (int i = 1; i <= n; ++i) {
if (s[i] == t[i]) {
dp[i][0] = min(dp[i - 1][0], min(get(prv[i], i - 1, 0) + 1, get(prv[i], i - 1, 1)));
dp[i][1] = inf;
lst = i;
} else {
dp[i][0] = min(get(prv[i], i - 1, 0), get(prv[i], i - 1, 1)) + 1;
dp[i][1] = min(get(lst, i - 1, 0), get(lst, i - 1, 1)) + 1;
}
// cerr << dp[i][0] << ' ' << dp[i][1] << endl;
update(i, 0, dp[i][0]);
update(i, 1, dp[i][1]);
}
cout << min(dp[n][0], dp[n][1]) << endl;
}
