#include<bits/stdc++.h>
using namespace std;
//#define int long long
int dp[1000100][8];
int inf=1e9;
int32_t main()
{
cin.tie(0);
cout.tie(0);
ios_base::sync_with_stdio(0);
int n;
cin>>n;
string a,b;
cin>>a>>b;
a='$'+a;
b='$'+b;
for(int i=0;i<=n;i++)
for(int j=0;j<6;j++)
dp[i][j]=inf;
dp[0][0]=0;
for(int i=1;i<=n;i++)
{
if(b[i]=='0')
dp[i][5]=min({dp[i-1][0]+2,dp[i-1][1]+1,dp[i-1][3]+1,dp[i-1][5]});
if(b[i]=='1')
dp[i][4]=min(dp[i-1][0]+1,dp[i-1][4]);
dp[i][4]=min(dp[i][4],dp[i][5]);
if(b[i]=='1')
dp[i][3]=min({dp[i-1][0]+2,dp[i-1][1]+1,dp[i-1][2]+1,dp[i-1][3]});
if(b[i]=='0')
dp[i][2]=min(dp[i-1][0]+1,dp[i-1][2]);
dp[i][2]=min({dp[i][2],dp[i][3]});
if(a[i]!=b[i])
dp[i][1]=min(dp[i-1][1],dp[i-1][0]+1);
dp[i][1]=min({dp[i][1],dp[i][3],dp[i][5]});
if(a[i]==b[i])
dp[i][0]=dp[i-1][0];
dp[i][0]=min({dp[i][0],dp[i][1],dp[i][2],dp[i][3],dp[i][4],dp[i][5]});
//cout<<i<<": "<<dp[i][0]<<" "<<dp[i][1]<<" "<<dp[i][2]<<" "<<dp[i][3]<<" "<<dp[i][4]<<" "<<dp[i][5]<<"\n";
}
cout<<dp[n][0];
return 0;
}
