// oooo
/*
har chi delet mikhad bebar ~
gitar o ba khodet nabar! ~
;Amoo_Hasan;
*/
#include<bits/stdc++.h>
//#pragma GCC optimize("O3,no-stack-protector,unroll-loops")
//#pragma GCC target("avx2,fma")
using namespace std;
typedef long long ll;
typedef long double ld;
#define Sz(x) int((x).size())
#define All(x) (x).begin(), (x).end()
#define wtf(x) cout<<#x <<" : " <<x <<endl
constexpr ll inf = 1e18, N = 1e6 + 10, mod = 1e9 + 7, pr = 1000696969;
int main() {
ios :: sync_with_stdio(0), cin.tie(0);
int n; cin >>n;
string A, B; cin >>A >>B;
for(int i = 0; i < n; i++) {
if(A[i] != '0') {
assert(0);
}
}
int ans = 0;
B.push_back('0');
for(int i = 1; i < Sz(B); i++) {
if(B[i] == '0' && B[i - 1] == '1') ans++;
}
cout<<ans;
return 0;
}
