#include <bits/stdc++.h>

#define int long long
#define ll long long
#define ld long double
#define endl '\n'
#define st first
#define nd second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
using namespace std;
int inf=1000000007;
ll infl=1000000000000000007;
ll mod=1000000007;
ll mod1=998244353;

const int N=1000007;

int DP[N][2];
int id[N];
bool is[N];

signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int n;
    cin>>n;
    string a,b;
    cin>>a>>b;
    a='#'+a,b='#'+b;
    int it=0;
    for(int i=1;i<=n;i++)
    {
        if(b[i]!=b[i-1]) it++;
        id[i]=it;
        if(a[i]!=b[i]) is[i]=1;
    }
    DP[0][1]=inf;
    for(int i=1;i<=n;i++)
    {
        DP[i][0]=inf,DP[i][1]=inf;
        if(!is[i])
        {
            DP[i][0]=min(DP[i-1][0],DP[i-1][1]);
        }
        else
        {
            DP[i][1]=min(DP[i-1][0]+1,DP[i-1][1]);
        }
        for(int j=0;j<i;j++)
        {
            int L=(id[i]-id[j+1]+1)/2+1;
            DP[i][0]=min(DP[i][0],DP[j][0]+L);
            DP[i][1]=min(DP[i][1],DP[j][1]+L);
        }
    }
    cout<<min(DP[n][0],DP[n][1]);
}