#include<bits/stdc++.h> using namespace std; int main(){ int n,a[1000005],b[20],ans; cin>>n; for(int i=1;i<=n;i++){ cin>>a[i]; b[a[i]%3]++; } ans=b[0]; ans+=min(b[1],b[2]); ans+=(max(b[1],b[2])-min(b[1],b[2]))/3; cout<<ans<<endl; return 0; }