// +-- -- --++-- +-In the name of ALLAH-+ --++-- -- --+ \\
/* Some Makoto Shinkai's :
“Who cares if we can't see any sunshine? I want you more than any blue sky!!!”
- Tenki no Ko
"By the time the date is over, the comet will be visible in the sky."
- Kimi no Nawa
“No matter what happens, even if the stars fall, I will live.”
- Byōsoku 5 Centimeter
*/
#include <bits/stdc++.h>
#define Raveluk ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define ll long long
#define ld long double
#define pb push_back
#define fi first
#define se second
#define pii pair<int,int>
#define tii tuple<int,int,int>
#define g1 get<0>
#define g2 get<1>
#define g3 get<2>
#define qf q.front()
#define all(x) (x).begin(), (x).end()
using namespace std;
int main()
{
Raveluk
int n,i,j,ans=1e9,k;
string a,b;
cin>>n>>a>>b;
int dp[n+1][4][4];
// 0 = off
// 1 = on
// 2 = invers
// 3 = ga ngapa ngapain
for(i=0;i<4;i++){
for(j=0;j<4;j++){
if(i == j or i == 3 or j == 3) dp[0][i][j] = 1;
else dp[0][i][j] = 2;
}
}
dp[0][3][3] = 0;
for(i=1;i<=n;i++){
int mn = 1e9;
//cout<<i<<" :\n";
for(j=0;j<4;j++){
for(k=0;k<4;k++){
mn = min(mn,dp[i-1][j][k]);
dp[i][j][k] = 1e9;
}
}
if(a[i-1] == b[i-1]){
// gaboleh invers (2)
// boleh ga ngapa ngapain (3)
if(b[i-1] == '1'){
// boleh on (1)
// gaboleh off (0)
// boleh apapun selama akhirnya -> on
// bisa juga off, terus invers [0][2]
dp[i][0][2] = min(dp[i-1][0][2],mn+2);
int nm = 1e9;
for(j=0;j<4;j++) nm = min(nm,dp[i-1][j][2]);
dp[i][0][2] = min(dp[i][0][2],nm+1);
//cout<<"off invers "<<dp[i][0][2]<<endl;
nm = 1e9;
for(j=0;j<4;j++) nm = min(nm,dp[i-1][j][1]);
dp[i][0][1] = min(dp[i-1][0][1],mn+2);
dp[i][0][1] = min(dp[i][0][1],nm+1);
dp[i][2][1] = min(dp[i-1][2][1],mn+2);
dp[i][2][1] = min(dp[i][2][1],nm+1);
for(j=0;j<4;j++) nm = min(nm,dp[i-1][1][j]);
dp[i][1][1] = min(dp[i-1][1][1],mn+1);
dp[i][1][1] = min(dp[i][1][1],nm);
dp[i][3][1] = min(dp[i-1][3][1],mn+1);
dp[i][3][1] = dp[i][1][3] = min(dp[i][3][1],nm);
//for(j=0;j<4;j++) cout<<j<<" "<<dp[i][j][1]<<endl;
}
else{
// gaboleh on (1)
// boleh off (0)
// boleh apapun selama akhirnya -> off
// bisa juga on, terus invers [1][2]
dp[i][1][2] = min(dp[i-1][1][2],mn+2);
int nm = 1e9;
for(j=0;j<4;j++) nm = min(nm,dp[i-1][j][2]);
dp[i][1][2] = min(dp[i][1][2],nm+1);
nm = 1e9;
//cout<<"on invers "<<dp[i][1][2]<<endl;
for(j=0;j<4;j++) nm = min(nm,dp[i-1][j][0]);
dp[i][1][0] = min(dp[i-1][1][0],mn+2);
dp[i][1][0] = min(dp[i][1][0],nm+1);
dp[i][2][0] = min(dp[i-1][2][0],mn+2);
dp[i][2][0] = min(dp[i][2][0],nm+1);
for(j=0;j<4;j++) nm = min(nm,dp[i-1][0][j]);
dp[i][0][0] = min(dp[i-1][0][0],mn+1);
dp[i][0][0] = min(dp[i][0][0],nm);
dp[i][3][0] = min(dp[i-1][3][0],mn+1);
dp[i][3][0] = dp[i][0][3] = min(dp[i][3][0],nm);
//for(j=0;j<4;j++) cout<<j<<" "<<dp[i][j][0]<<endl;
}
dp[i][3][3] = mn;
//cout<<dp[i][3][3]<<endl;
}
else{
// boleh invers (2)
// gaboleh ngapa ngapain (3)
if(b[i-1] == '1'){
// boleh on (1)
// gaboleh off (0)
// boleh apapun selama akhirnya -> on
// bisa juga off, terus invers [0][2]
dp[i][0][2] = min(dp[i-1][0][2],mn+2);
int nm = 1e9;
for(j=0;j<4;j++) nm = min(nm,dp[i-1][j][2]);
dp[i][0][2] = min(dp[i][0][2],nm+1);
//cout<<"off invers "<<dp[i][0][2]<<endl;
nm = 1e9;
for(j=0;j<4;j++) nm = min(nm,dp[i-1][j][1]);
dp[i][0][1] = min(dp[i-1][0][1],mn+2);
dp[i][0][1] = min(dp[i][0][1],nm+1);
dp[i][2][1] = min(dp[i-1][2][1],mn+2);
dp[i][2][1] = min(dp[i][2][1],nm+1);
for(j=0;j<4;j++) nm = min(nm,dp[i-1][1][j]);
dp[i][1][1] = min(dp[i-1][0][0],mn+1);
dp[i][1][1] = min(dp[i][0][0],nm);
dp[i][3][1] = min(dp[i-1][3][1],mn+1);
dp[i][3][1] = dp[i][1][3] = min(dp[i][3][1],nm);
//for(j=0;j<4;j++) cout<<j<<" "<<dp[i][j][1]<<endl;
}
else{
// gaboleh on (1)
// boleh off (0)
// boleh apapun selama akhirnya -> off
// bisa juga on, terus invers [1][2]
dp[i][1][2] = min(dp[i-1][1][2],mn+2);
int nm = 1e9;
for(j=0;j<4;j++) nm = min(nm,dp[i-1][j][2]);
dp[i][1][2] = min(dp[i][1][2],nm+1);
//cout<<"on invers "<<dp[i][1][2]<<endl;
nm = 1e9;
for(j=0;j<4;j++) nm = min(nm,dp[i-1][j][0]);
dp[i][1][0] = min(dp[i-1][1][0],mn+2);
dp[i][1][0] = min(dp[i][1][0],nm+1);
dp[i][2][0] = min(dp[i-1][2][0],mn+2);
dp[i][2][0] = min(dp[i][2][0],nm+1);
dp[i][3][0] = dp[i-1][3][0];
dp[i][0][3] = dp[i-1][0][3];
for(j=0;j<4;j++) nm = min(nm,dp[i-1][0][j]);
dp[i][0][0] = min(dp[i-1][0][0],mn+1);
dp[i][0][0] = min(dp[i][0][0],nm);
dp[i][3][0] = min(dp[i][3][0],mn+1);
dp[i][3][0] = dp[i][0][3] = min(dp[i][3][0],nm);
//for(j=0;j<4;j++) cout<<j<<" "<<dp[i][j][0]<<endl;
}
dp[i][3][2] = min(dp[i-1][3][2],mn+1);
int nm = 1e9;
for(j=0;j<4;j++) nm = min(nm,dp[i-1][j][2]);
dp[i][3][2] = min(dp[i][3][2],nm);
dp[i][2][3] = dp[i][3][2];
for(j=0;j<4;j++) nm = min(nm,dp[i-1][2][j]);
dp[i][2][2] = min(dp[i-1][2][2],mn+1);
dp[i][2][2] = min(dp[i-1][2][2],nm);
//cout<<dp[i][2][2]<<" "<<dp[i][3][2]<<endl;
}
}
for(i=0;i<4;i++){
for(j=0;j<4;j++) ans = min(ans,dp[n][i][j]);
}
cout<<ans;
return 0;
}
