#pragma GCC optimize("unroll-loops")
#include <algorithm>
#include <iostream>
#include <numeric>
#include <cstring>
#include <iomanip>
#include <vector>
#include <bitset>
#include <stack>
#include <queue>
#include <cmath>
#include <set>
#include <map>
#define endl '\n'
#define X first
#define Y second
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
const int maxn = 1e6+10;
const int inf = 1e9;
int dp[maxn][2][3];
int mnt[maxn][2];
int mna[maxn][3];
int mno[maxn];
char s[maxn];
char t[maxn];
int32_t main()
{
ios::sync_with_stdio(false);
cin.tie(0);
for(int i = 0; i < maxn; i++)
for(int j = 0; j < 2; j++)
for(int k = 0; k < 3; k++)
dp[i][j][k] = inf;
{
int i = 0;
dp[i][0][0] = 0;
mnt[i][0] = min(dp[i][0][0], min(dp[i][0][1], dp[i][0][2]));
mnt[i][1] = min(dp[i][1][0], min(dp[i][1][1], dp[i][1][2]));
mno[i] = min(mnt[i][0], mnt[i][1]);
for(int k = 0; k < 3; k++)
mna[i][k] = min(dp[i][0][k], dp[i][1][k]);
}
int n; cin >> n;
cin >> (s+1);
cin >> (t+1);
for(int i = 1; i <= n; i++)
{
if(s[i] == t[i])
{
dp[i][0][0] = mno[i-1];
dp[i][1][0] = inf;
}
else
{
dp[i][0][0] = inf;
dp[i][1][0] = min(mnt[i-1][1], mno[i-1]+1);
}
//
if(t[i] == '1')
{
dp[i][0][1] = inf;
dp[i][0][2] = min(mno[i-1]+1, mna[i-1][2]);
dp[i][1][1] = min( min(mnt[i-1][1]+1, mna[i-1][1]+1), min(dp[i-1][1][1], 2+mno[i-1]) );
dp[i][1][2] = inf;
}
else
{
dp[i][0][1] = min(mno[i-1]+1, mna[i-1][1]);
dp[i][0][2] = inf;
dp[i][1][1] = inf;
dp[i][1][2] = min( min(mnt[i-1][1]+1, mna[i-1][2]+1), min(dp[i-1][1][2], 2+mno[i-1]) );
}
//
mnt[i][0] = min(dp[i][0][0], min(dp[i][0][1], dp[i][0][2]));
mnt[i][1] = min(dp[i][1][0], min(dp[i][1][1], dp[i][1][2]));
mno[i] = min(mnt[i][0], mnt[i][1]);
for(int k = 0; k < 3; k++)
mna[i][k] = min(dp[i][0][k], dp[i][1][k]);
//cerr << dp[i][0][0] << " " << dp[i][0][1] << " " << dp[i][0][2] << endl;
//cerr << dp[i][1][0] << " " << dp[i][1][1] << " " << dp[i][1][2] << endl;
//cerr << "---- " << (s[i] == t[i]) << endl;
}
cout << mno[n] << endl;
return 0;
}
