//####################
//Lamps
//####################
#include <algorithm>
#include<bits/stdc++.h>
#include <utility>
using namespace std;
string A,B;
const int inf = 2*1e6;
#define pb push_back
#define SET0 1
#define SET1 2
#define FLIP 3
void dbg(vector<int> d){
for(int i:d){
if(i==SET0)cout<<"set0 ;";
if(i==SET1)cout<<"set1 ;";
if(i==FLIP)cout<<"flip ;";
}
cout<<endl;
}
bool apply(bool r,int m){
if(m==SET0)return 0;
if(m==SET1)return 1;
if(m==FLIP)return r^1;
return r;
}
signed main(){
ios::sync_with_stdio(false);
cin.tie();
int n; cin >> n;
cin >> A >> B;
int dp[n+1][4][4];
for(int a=0;a<=3;a++)for(int b=0;b<=3;b++)dp[n][a][b]=0;
vector<pair<int,int>> t;
for(int a=0;a<=3;a++)for(int b=0;b<=3;b++)t.pb(make_pair(a,b));
for(int pos = n-1;pos>=0;pos--){
for(int i1 = 0 ; i1<= 3;i1++)
for(int i2 = 0 ; i2 <= 3;i2++){
dp[pos][i1][i2] = 2*n+1;
for(auto p:t){
bool r = A[pos]-'0';
r = apply(r,p.first);
r = apply(r,p.second);
if(r!=(bool)(B[pos]-'0'))continue;
int c=2;
if(i1==p.second && p.first==0 && i2==0){
c=0;
}else{
if(i1==p.first || p.first==0)c--;
if(i2==p.second|| p.second==0)c--;
}
dp[pos][i1][i2] = min(dp[pos][i1][i2],c+dp[pos+1][p.first][p.second]);
}
}
}
cout<<dp[0][0][0]<<endl;
return 0;
};
