#include <bits/stdc++.h>
using namespace std;
#define TRACE(x) cerr << #x << " :: " << x << endl
#define _ << " " <<
#define SZ(x) (int)(x).size()
#define ALL(x) (x).begin(),(x).end()
#define FOR(i,a,b) for(int i=(a);i<=(b);++i)
#define RFOR(i,a,b) for (int i=(a);i>=(b);--i)
#define chmin(x,y) x = min(x,y)
const int mxN = 1e6+5;
int N;
string A, B;
int dp[mxN][6];
int main() {
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin >> N >> A >> B;
FOR(x,0,5) dp[N][x] = 0;
RFOR(i,N-1,0){
if (A[i] == B[i]) FOR(x,0,5) dp[i][x] = dp[i+1][0];
else FOR(x,0,5) dp[i][x] = dp[i+1][1] + (x!=1);
if (B[i] == '0') {
chmin(dp[i][0], dp[i+1][2]+1);
chmin(dp[i][1], dp[i+1][2]+1);
chmin(dp[i][2], dp[i+1][2]);
chmin(dp[i][3], dp[i+1][2]);
chmin(dp[i][4], dp[i+1][4]);
chmin(dp[i][5], dp[i+1][4]+1);
} else {
chmin(dp[i][0], dp[i+1][5]+1);
chmin(dp[i][1], dp[i+1][5]+1);
chmin(dp[i][2], dp[i+1][3]+1);
chmin(dp[i][3], dp[i+1][3]);
chmin(dp[i][4], dp[i+1][5]);
chmin(dp[i][5], dp[i+1][5]);
}
//~ cout << i << " :: ";
//~ FOR(x,0,3) cout << dp[i][x] << ' ';
//~ cout << endl;
}
cout << dp[0][0] << '\n';
}
