#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1000005;
using pi = pair<int, int>;
int n;
char s[MAXN], t[MAXN];
int dp[MAXN][5];
int getCost(int x, int p){
char c = x + '0';
if(c == '2') c = s[p];
return c != t[p];
}
int moveCost(int p1, int p2, int x1, int x2){
x1 /= 2, x2 /= 2;
int arg1 = getCost(x1, p1) != getCost(x2, p2);
int arg2 = x1 != x2;
return arg1 + arg2;
}
int adj[5][5] = {
{1, 0, 1, 0, 1},
{0, 1, 0, 1, 1},
{1, 0, 1, 0, 1},
{0, 1, 0, 1, 1},
{1, 0, 0, 1, 1}};
int main(){
scanf("%d %s %s",&n,s+1,t+1);
fill(dp[0], dp[0] + 4, 1e9);
t[0] = '0'; t[n+1] = '0';
s[0] = '0', s[n+1] = '0';
for(int i=1; i<=n+1; i++){
for(int j=0; j<5; j++){
dp[i][j] = 1e9;
for(int k=0; k<5; k++){
if(!adj[k][j]) continue;
dp[i][j] = min(dp[i][j], dp[i-1][k] + moveCost(i-1, i, k, j) + (j == 4 && (k == 1 || k == 2)));
}
}
}
cout << dp[n+1][4] / 2<< endl;
}
