#include<bits/stdc++.h> using namespace std; int n,sum,a[100005],y11,y22; int main(){ scanf("%d",&n); for(int i=1;i<=n;i++){ scanf("%d",&a[i]); if(a[i]%3==0)sum++; if(a[i]%3==1)y11++; if(a[i]%3==2)y22++; } int t=min(y11,y22); sum+=t; y11-=t,y22-=t; if(y11!=0){ sum+=y11/3; } else{ sum+=y22/3; } printf("%d",sum); return 0; }