#include <iostream>
using namespace std;
int n, u, d, t, x;
int main() {
cin >> n;
u = 0;
d = 0;
t = 0;
for(int i=1; i<=n; i++){
cin >> x;
if(x == 1){
u = u+1;
}else{
if(x == 2){
d = d+1;
}else{
if(x == 3){
t = t+1;
}
}
}
}
for(int i=1; i<=n; i++){
cin >> x;
if(x == 1){
u = u+1;
}else{
if(x == 2){
d = d+1;
}else{
if(x == 3){
t = t+1;
}
}
}
}
u = u/4;
d = d/4;
t = t/4;
cout << u+d+t;
return 0;
}
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