//####################
//LAMP-JOI2019
//####################
#include<bits/stdc++.h>
using namespace std;
int n;
string a,b;
const int RIEN = 0;
const int FLIP = 1;
const int ZERO = 2;
const int ONE = 3;
const int ONE_ZERO = 4;
const int ZERO_ONE = 5;
const int maxiNode = 1000000;
int dp[maxiNode][6];
int solve(int pos,int state){
if(pos<n && dp[pos][state]!=-1)return dp[pos][state];
if(pos==n){
return 0;
}else{
int ans = n+1;
if(state==RIEN){
ans = min(ans,1+solve(pos+1,ZERO)+(b[pos]=='1'?n+1:0));
ans = min(ans,1+solve(pos+1,ONE)+(b[pos]=='0'?n+1:0));
ans = min(ans,1+solve(pos+1,FLIP)+(b[pos]==a[pos]?n+1:0));
}else if(state == FLIP){
ans = min(ans, solve(pos+1,FLIP) + (b[pos]==a[pos]?n+1:0));
ans = min(ans,1+solve(pos+1,ZERO)+(b[pos]=='1'?n+1:0));
ans = min(ans,1+solve(pos+1,ONE)+(b[pos]=='0'?n+1:0));
}else if(state == ZERO){
ans = min(ans,solve(pos+1,ZERO)+(b[pos]=='1'?n+1:0));
ans = min(ans,1+solve(pos+1,ZERO_ONE)+(b[pos]=='0'?n+1:0));
ans = min(ans,1+solve(pos+1,FLIP)+(b[pos]==a[pos]?n+1:0));
}else if(state == ONE){
ans = min(ans,solve(pos+1,ONE)+(b[pos]=='0'?n+1:0));
ans = min(ans,1+solve(pos+1,ONE_ZERO)+(b[pos]=='1'?n+1:0));
ans = min(ans,1+solve(pos+1,FLIP)+(b[pos]==a[pos]?n+1:0));
}else if(state == ZERO_ONE){
ans = min(ans,solve(pos+1,ZERO)+(b[pos]=='1'?n+1:0));
ans = min(ans,solve(pos+1,ONE)+(b[pos]=='0'?n+1:0));
ans = min(ans,solve(pos+1,ZERO_ONE)+(b[pos]=='0'?n+1:0));
ans = min(ans,1+solve(pos+1,FLIP)+(b[pos]==a[pos]?n+1:0));
}else if(state==ONE_ZERO){
ans = min(ans,solve(pos+1,ZERO)+(b[pos]=='1'?n+1:0));
ans = min(ans,solve(pos+1,ONE)+(b[pos]=='0'?n+1:0));
ans = min(ans,solve(pos+1,ONE_ZERO)+(b[pos]=='1'?n+1:0));
ans = min(ans,1+solve(pos+1,FLIP)+(b[pos]==a[pos]?n+1:0));
}
if(a[pos]==b[pos]){
ans=min(ans, solve(pos+1,RIEN));
}
return dp[pos][state]=ans;
}
}
signed main(){
for(int i = 0;i<maxiNode;i++){
for(int j = 0;j<6;j++){
dp[i][j] = -1;
}
}
ios::sync_with_stdio(false);
cin.tie(0);
cin>>n;
cin>>a>>b;
cout<<solve(0,RIEN)<<endl;
return 0;
};
