#include<bits/stdc++.h> using namespace std; int main(){ int n,a[100001]={},cnt=0,c1=0,c2=0; cin>>n; for(int i=0;i<n;i++){ cin>>a[i]; if(a[i]%3==0){ cnt++; a[i]=0; } if(a[i]%3==1){ c1++; } if(a[i]%3==2){ c2++; } } cnt+=min(c1,c2); c1-=min(c1,c2); c2-=min(c1,c2); cnt+=c1/3; cnt+=c2/3; cout<<cnt; return 0; }