#include <bits/stdc++.h>
using namespace std;

int main() {
	int arr[]= {2,2,5,5,3,3};
	int n=sizeof(arr)/sizeof(arr[0]);
	int pairs=0;
	unordered_map<int, int> mp;
	for(int j=0;j<n;j++){
		int rem=arr[j]%5;
		if(mp.find((5-rem)%5)!=mp.end()){
			pairs+=mp[(5-rem)%5];
		}
		mp[rem]++;
	}
	cout<<pairs;
	return 0;
}