#include <bits/stdc++.h>
typedef long long ll;
using namespace std;
string x, y;
int dp0[1001000], dp1[1001000][3], dp2[1001000][3][3], ans[1001000], dp2mn[1001000][3];
void getmn(int x){
for (int i=0;i<3;i++){
ans[x] = min(ans[x], dp1[x][i]);
for (int j=0;j<3;j++){
dp2mn[x][i] = min(dp2mn[x][i], dp2[x][i][j]);
dp2mn[x][j] = min(dp2mn[x][j], dp2[x][i][j]);
ans[x] = min(ans[x], dp2[x][i][j]);
}
}
ans[x] = min(ans[x], dp0[x]);
}
int main(){
cin.tie(NULL);
ios_base::sync_with_stdio(false);
int n;
cin >> n >> x >> y;
for (int i=0;i<n;i++){
dp0[i] = 1e9;
ans[i] = 1e9;
fill(dp1[i], dp1[i]+3, 1e9);
fill(dp2mn[i], dp2mn[i]+3, 1e9);
for (int j=0;j<3;j++) fill(dp2[i][j], dp2[i][j]+3, 1e9);
}
if (x[0]==y[0]) dp0[0] = 0, dp2[0][2][2] = 2;
else dp1[0][2] = 1, dp2[0][0][2] = 2, dp2[0][1][2] = 2;
dp1[0][y[0]-'0'] = 1;
for (int j=0;j<3;j++) dp2[0][j][y[0]-'0'] = 2;
dp2[0][(y[0]-'0')^1][2] = 2;
getmn(0);
for (int i=1;i<n;i++){
if (x[i]==y[i]) dp0[i] = ans[i-1];
else dp1[i][2] = min(ans[i-1]+1, min(dp1[i-1][2], dp2mn[i-1][2]));
dp1[i][y[i]-'0'] = min(ans[i-1]+1, min(dp1[i-1][y[i]-'0'], dp2mn[i-1][y[i]-'0']));
for (int j=0;j<3;j++){
int val1 = min(min(dp1[i-1][j], dp1[i-1][y[i]-'0']), min(dp2mn[i-1][j], dp2mn[i-1][y[i]-'0']));
dp2[i][j][y[i]-'0'] = min(ans[i-1]+2, min(val1+1, dp2[i-1][j][y[i]-'0']));
}
int val = min(min(dp1[i-1][2], dp1[i-1][(y[i]-'0')^1]), min(dp2mn[i-1][2], dp2mn[i-1][(y[i]-'0')^1]));
dp2[i][(y[i]-'0')^1][2] = min(ans[i-1]+2, min(val+1, dp2[i-1][(y[i]-'0')^1][2]));
if (x[i]==y[i]){
int val2 = min(dp1[i-1][2], dp2mn[i-1][2]);
dp2[i][2][2] = min(ans[i-1]+2, min(val2+1, dp2[i-1][2][2]));
}
getmn(i);
}
/*
for (int i=0;i<n;i++) printf("%d ", dp0[i]);
printf("\n\n");
for (int j=0;j<3;j++){
for (int i=0;i<n;i++) printf("%d ", dp1[i][j]);
printf("\n");
}
printf("\n");
for (int j=0;j<3;j++){
for (int k=0;k<3;k++){
for (int i=0;i<n;i++) printf("%d ", dp2[i][j][k]);
printf("\n");
}
}
printf("\n");
for (int i=0;i<n;i++) printf("%d ", ans[i]);
printf("\n\n");
*/
cout << ans[n-1];
return 0;
}
