#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];
int id[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;
    vector<pair<int,int>>V;
    int l=-1,it=0;
    for(int i=1;i<=n;i++)
    {
        if(b[i]!=b[i-1]) it++;
        id[i]=it;
       // cout<<id[i]<<" ";
        if(a[i]!=b[i])
        {
            if(l==-1) l=i;
        }
        else if(l!=-1)
        {
            V.pb({l,i-1});
            l=-1;
        }
    }
   // cout<<endl;
    if(l!=-1) V.pb({l,n});
   // for(auto [a,b]:V) cout<<a<<" "<<b<<endl;
    int m=sz(V);
    //cout<<m<<endl;
    for(int i=1;i<=m;i++)
    {
        DP[i]=DP[i-1];
        for(int j=0;j<i;j++)
        {
            DP[i]=max(DP[i],DP[j]+(i-j)-(id[V[i-1].nd]-id[V[j].st]+1)/2-1);
        }
    }
    cout<<m-DP[m];
}