第一题0，第二题AC，心碎了一地
int r[15][10];
int c[10];
int count(int n){
	int cnt = 0;
	while (n){
		cnt++;
		n /= 10;
	}
	return cnt;
}
long long getnum(int n, int m){
	long long res = n;
	while (m--)
		res *= 10;
	return res;
}
int main(){
	int n;
	cin >> n;
	vector<int> a(n);
	for (int i = 0; i < n; i++){
		cin >> a[i];
		r[count(a[i])][a[i] % 7]++;
		c[a[i] % 7]++;
	}
	long long res = 0;
	for (int i = 1; i <= 9; i++){
		for (int j = 0; j <= 6; j++){
			if (r[i][j] == 0)continue;
			for (int k = 0; k <= 6; k++){
				if (c[k] == 0)continue;
				long long tmp = getnum(k, i) + j;
				if (tmp % 7 == 0){
					if(j==k)res += r[i][j] * (c[k] - 1);
					else res += r[i][j] * c[k];
				}
			}
		}
	}
	cout << res << endl;
}