#include<bits/stdc++.h> using namespace std; typedef long long ll; int main(){ ll n,l1=0,l2=0,ans=0; cin>>n; for(ll i=1;i<=n;i++){ ll x; cin>>x; if(x%3==0){ ans++; }else if(x%3==1){ l1++; }else{ l2++; } } if(l1>l2){ ans+=l2; l1-=l2; ans+=l1/3; }else{ ans+=l1; l2-=l1; ans+=l2/3; } cout<<ans<<endl; return 0; }