#include<bits/stdc++.h>
using namespace std;
int dp[2][4][4][4], dp1[2][4], dp2[2][4][4];
int main() {
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
int n;
string s, t;
cin>>n>>s>>t;
for(int i=0; i<=1; ++i) {
for(int a=0; a<=3; ++a) {
for(int b=0; b<=3; ++b) {
for(int c=0; c<=3; ++c) {
dp[i][a][b][c] = n;
}
}
}
}
dp[0][0][0][0]=0;
for(int a=1; a<=3; ++a) {
dp1[0][a]=n;
for(int b=1; b<=3; ++b) {
dp2[0][a][b]=n;
}
}
for(int i=1; i<=n; ++i) {
int v1 = n;
for(int a=0; a<=3; ++a) {
for(int b=0; b<=3; ++b) {
for(int c=0; c<=3; ++c) {
dp[i%2][a][b][c]=n;
v1 = min(v1, dp[(i+1)%2][a][b][c]);
}
}
}
if(s[i-1]==t[i-1]) {
dp[i%2][0][0][0] = v1;
}
for(int a=1; a<=3; ++a) {
if((a==1 && t[i-1]=='0') || (a==2 && t[i-1]=='1') || (a==3 && s[i-1]!=t[i-1])) {
dp[i%2][a][0][0] = min(v1+1, dp1[(i+1)%2][a]);
}
for(int b=1; b<=3; ++b) {
if(b==a) continue;
if((a==1 && t[i-1]=='0') || (a==2 && t[i-1]=='1') || (a==3 && ((b==1 && t[i-1]=='1') || (b==2 && t[i-1]=='0')))) {
dp[i%2][a][b][0] = min(v1+2, min(dp1[(i+1)%2][a], dp1[(i+1)%2][b])+1);
dp[i%2][a][b][0] = min(dp[i%2][a][b][0], dp2[(i+1)%2][a][b]);
}
else {
continue;
}
for(int c=1; c<=3; ++c) {
if(c==a || c==b) continue;
dp[i%2][a][b][c] = min(v1+3, min(dp1[(i+1)%2][a], min(dp1[(i+1)%2][b], dp1[(i+1)%2][c]))+2);
dp[i%2][a][b][c] = min(dp[i%2][a][b][c], min(dp2[(i+1)%2][a][b], min(dp2[(i+1)%2][a][c], dp2[(i+1)%2][b][c]))+1);
dp[i%2][a][b][c] = min(dp[i%2][a][b][c], dp[(i+1)%2][a][b][c]);
}
}
}
for(int a=1; a<=3; ++a) {
dp1[i%2][a]=n;
for(int j=0; j<=3; ++j) {
for(int k=0; k<=3; ++k) {
dp1[i%2][a] = min(dp1[i%2][a], dp[i%2][a][j][k]);
dp1[i%2][a] = min(dp1[i%2][a], dp[i%2][j][a][k]);
dp1[i%2][a] = min(dp1[i%2][a], dp[i%2][j][k][a]);
}
}
for(int b=1; b<=3; ++b) {
dp2[i%2][a][b]=n;
for(int j=0; j<=3; ++j) {
dp2[i%2][a][b] = min(dp2[i%2][a][b], dp[i%2][a][b][j]);
dp2[i%2][a][b] = min(dp2[i%2][a][b], dp[i%2][j][a][b]);
}
}
}
}
int ans = n;
for(int a=0; a<=3; ++a) {
for(int b=0; b<=3; ++b) {
for(int c=0; c<=3; ++c) {
ans = min(ans, dp[n%2][a][b][c]);
}
}
}
cout<<ans;
}
