#include <bits/stdc++.h>
using namespace std;
int dp[1000005], dp1[1000005], dp2[1000005], mindp1[1000005], mindp2[1000005], ind[1000005];
vector<int> vec;
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n, sz=0, state=0;
cin >> n;
string s, t;
cin >> s >> t;
vec.push_back(0);
for (int i=0; i<n; i++)
{
if (i && t[i]!=t[i-1])
{
sz++;
vec.push_back(state);
ind[sz]=(state==2?ind[sz-1]:sz);
state=0;
}
if (state%2==0 && s[i]==t[i])
state++;
else if (state<2 && s[i]!=t[i])
state+=2;
}
sz++;
vec.push_back(state);
ind[sz]=(state==2?ind[sz-1]:sz);
for (int i=1; i<=sz; i++)
{
if (i&1)
dp[i]=mindp1[i-1]+i/2+1;
else
dp[i]=mindp2[i-1]+i/2+1;
dp[i]=min(dp[i], dp[ind[i]]+(i-ind[i])/2+1);
if (vec[i]==1)
dp[i]=min(dp[i], dp[i-1]);
dp1[i]=dp[i]-i/2;
dp2[i]=dp[i]-(i+1)/2;
mindp1[i]=min(mindp1[i-1], dp1[i]);
mindp2[i]=min(mindp2[i-1], dp2[i]);
}
cout << dp[sz];
}
