#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) (int)a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x,y) ((x+y-1)/(y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl
#define rep(i,n) for(int i = 0; i < n; ++i)
#define rep1(i,n) for(int i = 1; i <= n; ++i)
#define rev(i,s,e) for(int i = s; i >= e; --i)
#define trav(i,a) for(auto &i : a)
template<typename T>
void amin(T &a, T b) {
a = min(a,b);
}
template<typename T>
void amax(T &a, T b) {
a = max(a,b);
}
#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 42
#endif
/*
read some solutions a long time ago, remember some key ideas from there
*/
const int MOD = 1e9 + 7;
const int N = 1e5 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;
void solve(int test_case)
{
int n; cin >> n;
vector<int> a(n+5), b(n+5);
rep1(i,n){
char ch; cin >> ch;
a[i] = ch-'0';
}
rep1(i,n){
char ch; cin >> ch;
b[i] = ch-'0';
}
int m = 10;
int c[m][m];
auto get = [&](int x){
vector<int> v = {-1};
if(x == 1) v.pb(0);
if(x == 2) v.pb(1);
if(x == 3) v.pb(2);
if(x == 4) v.pb(0), v.pb(1);
if(x == 5) v.pb(0), v.pb(2);
if(x == 6) v.pb(1), v.pb(0);
if(x == 7) v.pb(1), v.pb(2);
if(x == 8) v.pb(2), v.pb(0);
if(x == 9) v.pb(2), v.pb(1);
return v;
};
rep(x,m){
rep(y,m){
auto v1 = get(x), v2 = get(y);
int dp[sz(v1)][sz(v2)];
memset(dp,0,sizeof dp);
rep1(i,sz(v1)-1){
rep1(j,sz(v2)-1){
dp[i][j] = max(dp[i][j-1],dp[i-1][j]);
if(v1[i] == v2[j]){
amax(dp[i][j],dp[i-1][j-1]+1);
}
}
}
int lcs = dp[sz(v1)-1][sz(v2)-1];
c[x][y] = sz(v2)-lcs-1;
}
}
int fv[m][2];
rep(j,m){
rep(k,2){
int x = k;
if(j == 1) x = 0;
if(j == 2) x = 1;
if(j == 3) x ^= 1;
if(j == 4) x = 0, x = 1;
if(j == 5) x = 0, x ^= 1;
if(j == 6) x = 1, x = 0;
if(j == 7) x = 1, x ^= 1;
if(j == 8) x ^= 1, x = 0;
if(j == 9) x ^= 1, x = 1;
fv[j][k] = x;
}
}
int dp[n+5][m];
memset(dp,0x3f,sizeof dp);
dp[1][0] = 0;
rep1(i,n){
rep(j,m){
rep(k,m){
int v = fv[k][a[i]];
if(v == b[i]){
amin(dp[i+1][k],dp[i][j]+c[j][k]);
}
}
}
}
int ans = inf1;
rep(j,m) amin(ans,dp[n+1][j]);
cout << ans << endl;
}
int main()
{
fastio;
int t = 1;
// cin >> t;
rep1(i, t) {
solve(i);
}
return 0;
}
