#include<bits/stdc++.h>
#define ll long long
#define pii pair<int,int>
using namespace std;
const int mxn=1e5+5;
const int inf=1e9;
int get(int x,int op) {
if(op == 0) return 0;
if(op == 1) return 1;
if(op == 2) return x ^ 1;
return x;
}
int op(int a) {
return a != 3;
}
int op(int a,int b) {
return (a != 3) + (b != 3);
}
int main() {
int n;
cin >> n;
int dp[n + 1][4][4][2] = {};
int a[n + 1];
int b[n + 1];
for(int i = 1; i <= n; i++) {
char c;
cin >> c;
c -= '0';
a[i] = c;
}
for(int i = 1; i <= n; i++) {
char c;
cin >> c;
c -= '0';
b[i] = c;
}
int lm0 = inf;
int lm1 = inf;
for(int i = 0; i < 4; i++) {
for(int j = 0; j < 4; j++) {
int x = get(a[1],i);
int y = get(x,j);
if(y == b[1]) {
dp[1][i][j][0] = op(i,j);
dp[1][i][j][1] = inf;
}
else {
dp[1][i][j][1] = op(i,j) + 1;
dp[1][i][j][0] = inf;
}
lm0 = min(lm0,dp[1][i][j][0]);
lm1 = min(lm1,dp[1][i][j][1]);
}
}
for(int i = 2; i <= n; i++) {
int cm0 = inf,cm1 = inf;
for(int j = 0; j < 4; j++) {
for(int k = 0; k < 4; k++) {
int x = get(a[i],j);
int y = get(x,k);
if(y != b[i]) {
dp[i][j][k][0] = inf;
int &r = dp[i][j][k][1];
r = dp[i - 1][j][k][1];
r = min(r,lm1 + op(j,k));
for(int x = 0; x < 4; x++) r = min(r,min(dp[i - 1][x][j][0] + 1,dp[i - 1][x][j][1]) + op(k));
for(int x = 0; x < 4; x++) r = min(r,min(dp[i - 1][j][x][0] + 1,dp[i - 1][j][x][1]) + op(k));
cm1 = min(cm1,dp[i][j][k][1]);
}
else {
dp[i][j][k][1] = inf;
int &r = dp[i][j][k][0];
r = dp[i - 1][j][k][0];
r = min(r,min(lm0,lm1) + op(j,k));
for(int x = 0; x < 4; x++) r = min(r,min(dp[i - 1][x][j][0],dp[i - 1][x][j][1]) + op(k));
for(int x = 0; x < 4; x++) r = min(r,min(dp[i - 1][j][x][0],dp[i - 1][j][x][1]) + op(k));
cm0 = min(cm0,dp[i][j][k][0]);
}
}
}
lm0 = cm0;
lm1 = cm1;
}
cout<<min(lm0,lm1)<<endl;
}
