#include <bits/stdc++.h>
typedef long long ll;
using namespace std;
string x, y;
int dp[1001000][3], ans[1001000];
int main(){
cin.tie(NULL);
ios_base::sync_with_stdio(false);
int n;
cin >> n >> x >> y;
if (x[0]==y[0]){
if (y[0]=='0') dp[0][0] = 1, dp[0][1] = 2;
else dp[0][0] = 2, dp[0][1] = 1;
dp[0][2] = 2;
}
else{
if (y[0]=='0') dp[0][0] = 1, dp[0][1] = 2;
else dp[0][0] = 2, dp[0][1] = 1;
dp[0][2] = 1;
ans[0] = 1;
}
for (int i=1;i<n;i++){
if (y[i]==y[i-1]) dp[i][0] = dp[i-1][0], dp[i][1] = dp[i-1][1];
else dp[i][y[i]-'0'] = dp[i-1][y[i]-'0'], dp[i][(y[i]-'0')^1] = dp[i-1][(y[i]-'0')^1]+1;
dp[i][y[i]-'0'] = min(dp[i][y[i]-'0'], ans[i-1]+1);
dp[i][(y[i]-'0')^1] = min(dp[i][(y[i]-'0')^1], ans[i-1]+2);
if (x[i]!=y[i]){
dp[i][2] = min(dp[i-1][2], ans[i-1]+1);
ans[i] = min(ans[i-1]+1, min(dp[i][0], min(dp[i][1], dp[i][2])));
}
else{
dp[i][2] = min(ans[i-1]+2, min(dp[i-1][2], dp[i-1][(y[i]-'0')^1])+1);
ans[i] = ans[i-1];
}
}
/*for (int i=0;i<n;i++) printf("%d", dp[i][0]);
printf("\n");
for (int i=0;i<n;i++) printf("%d", dp[i][1]);
printf("\n");
for (int i=0;i<n;i++) printf("%d", dp[i][2]);
printf("\n");
for (int i=0;i<n;i++) printf("%d", ans[i]);
printf("\n");*/
cout << ans[n-1];
return 0;
}
