#include <bits/stdc++.h>
#define fir first
#define sec second
#define ll long long
#define pll pair<ll, ll>
using namespace std;
const int mxN=1000100;
const int INF=10000001;
int N;
char A[mxN], B[mxN];
int state[mxN][5], dp[mxN][5];
int adj[5][5]={{0, 1, 1, 2, 2}, {0, 0, 1, 1, 2}, {0, 1, 0, 2, 1}, {0, 0, 1, 0, 4}, {0, 1, 0, 4, 0}};
int main()
{
cin.tie(0);
ios::sync_with_stdio(false);
cin >> N;
cin >> A+1;
cin >> B+1;
for(int i=1;i<=N;i++)
{
if(B[i]=='0') state[i][2]=state[i][3]=1;
else state[i][1]=state[i][4]=1;
if(A[i]!=B[i]) state[i][0]=1;
}
dp[0][1]=dp[0][2]=dp[0][3]=dp[0][4]=INF;
for(int i=1;i<=N;i++)
{
for(int j=0;j<5;j++) dp[i][j]=INF;
for(int j=0;j<5;j++)
{
for(int k=0;k<5;k++)
{
int tmp=dp[i-1][k]+adj[k][j];
if(state[i-1][k]==0 && state[i][j]==1) tmp++;
dp[i][j]=min(dp[i][j], tmp);
}
}
}
//for(int i=1;i<=N;i++) for(int j=0;j<5;j++) printf("dp[%d][%d]=%d\n", i, j, dp[i][j]);
int ans=INF;
for(int i=0;i<5;i++)
{
ans=min(ans, dp[N][i]);
}
cout << ans;
}
