//https://www.instagram.com/_modwwe/
#pragma GCC optimize("Ofast,unroll-loops")
//#pragma GCC target("avx2,bmi,bmi2")
#include<bits/stdc++.h>
//#define int long long
//#define ll long long
#define down cout<<'\n';
#define NHP ios_base::sync_with_stdio(0);cout.tie(0);cin.tie(0);
#define modwwe int t;cin>>t; while(t--)
#define bit(i,j) (i>>j&1)
#define sobit(a) __builtin_popcountll(a)
#define task "test"
#define fin(x) freopen(x".inp","r",stdin)
#define fou(x) freopen(x".out","w",stdout)
#define pb push_back
#define checktime cerr << (double)clock() / CLOCKS_PER_SEC * 1000 << " ms";
using namespace std;
void phongbeo();
const int inf=1e18;
const int mod2=1e9+7;
const int mod1=998244353;
struct icd
{
int a,b;
};
struct ib
{
int a;
int b;
};
struct ic
{
int a,b,c;
};
struct id
{
int a,b,c,d;
};
struct ie
{
int a,b,c, d,e,f;
};
int n,m,s1,s2,s4,s3,sf,k,r,mid,s5,s6,mx,s7,s8,s9,mx2,res,dem2=0,dem=0,l;
int i,s10,s12;
int el=29;
main()
{
#ifndef ONLINE_JUDGE
/// fin(task),fou(task);
#endif
NHP
/// cin>>s1;
// modwwe
phongbeo(),down
}
string a,b;
int dp[4][4];
char as(char s,int x)
{
if(x==0) return s;
if(x==1) return '0';
if(x==2) return '1';
if(x==3&&s=='0') return '1';
else return '0';
}
void phongbeo()
{
cin>>n;
///a[0][0]->0
cin>>a>>b;
a=" "+a;
b=" "+b;
for(int j=0; j<4; j++)
for(int z=0; z<4; z++)
dp[j][z]=n+1;
dp[0][0]=0;
for(int i=1; i<=n; i++)
{
for(int j=0; j<4; j++)
for(int z=0; z<4; z++)
dp[0][0]=min(dp[j][z],dp[0][0]),
dp[j][0]=min(dp[j][0],dp[j][z]),
dp[0][z]=min(dp[0][z],dp[j][z]);
for(int z=1; z<4; z++)
dp[0][z]=min(dp[0][z],dp[0][0]+1),
dp[z][0]=min(dp[z][0],dp[0][0]+1);
for(int j=1; j<4; j++)
for(int z=1; z<4; z++)
dp[j][z]=min({dp[0][0]+2,dp[j][z],dp[0][z]+1,dp[j][0]+1});
for(int j=0; j<4; j++)
for(int z=0; z<4; z++)
{
char s=a[i];
s=as(s,j);
s=as(s,z);
if(s!=b[i])
dp[j][z]=n+1;
}
}
s2=n+1;
for(int j=0; j<4; j++)
for(int z=0; z<4; z++)
s2=min(s2,dp[j][z]);
cout<<s2;
}
