//Pb1
#include <iostream>
using namespace std;

void citire(int &n, int a[])
{
	cin >> n;
	for(int i = 1; i <= n; ++i)
		cin >> a[i];
}


int cifEgale(int n)
{
	int uc = n % 10;
	n /= 10;
	while(n > 0)
	{
		if(uc != n % 10)
			return 0;
		n /= 10;
	}
	return 1;

}

int cateEgale(int n, int a[])
{
	int cnt = 0;
	for(int i = 1; i < n; ++i)
		for(int j = i + 1; j <= n; ++j)
			if(cifEgale(a[i] + a[j]))
				cnt++;
	return cnt;
}

int main()
{
	int n, a[100001];
	citire(n, a);
	cout << cateEgale(n, a);
}