#include<bits/stdc++.h>
using namespace std;
const int INF=(1<<30);
int dp[10]={INF,INF,INF,INF,INF,INF,INF,INF,0,INF},clo[10];
bool f(){
char c;
cin >> c;
return (c=='1');
}
void minn(int &a, int b){
a=min(a,b);
}
void d(int k,vector<int> p,vector<int> q){
for(int i=0;i<p.size();i++){
minn(dp[k],clo[p[i]]+q[i]);
}
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int n;
cin >> n;
bool a[n+2],b[n+2];
for(int i=1;i<=n;i++){
a[i]=f();
}
for(int i=1;i<=n;i++){
b[i]=f();
}
n++; a[n]=0; b[n]=0;
for(int i=1;i<=n;i++){
for(int j=0;j<=9;j++){
clo[j]=dp[j];
dp[j]=INF;
}
if(a[i]==b[i]) d(8,{0,1,2,3,4,5,6,7,8,9},{0,0,0,-1,0,-1,0,0,0,0});
else d(9,{0,1,2,3,4,5,6,7,8,9},{1,0,0,0,0,0,1,0,1,0});
if(!b[i]){
d(0,{0,2,8},{0,0,1});
d(1,{1,3,9},{0,0,1});
d(4,{4,6},{0,1});
d(5,{5,7},{0,1});
}
else{
d(2,{0,2},{1,0});
d(3,{1,3},{1,0});
d(6,{4,6,8},{0,0,1});
d(7,{5,7,9},{0,0,1});
}
//for(int j=0;j<=9;j++) cout << dp[j] << ' ';
//cout << '\n';
}
cout << dp[8] << '\n';
}
