#include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define printVec(v) printf("{"); for (const auto& i : v) { std::cout << i << ", "; } printf("}\n");
#define degreeToRadian(deg) (((deg)/360)*2*M_PI)
#define radianTodegree(rad) (((rad)/2/M_PI)*360)
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
using namespace std;
using P = pair<int,int>;
using ll = long long;
const ll INF = 1LL<<60;
const int MOD = 1e9 + 7;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};

//cin.tie(0);ios::sync_with_stdio(false);
//cout << fixed << setprecision(15) << y << endl;

//数字根
int digital_root (string ss) {
  while (ss.size() > 1) {
    ss = ss.substr(2, ss.size()) + to_string((ss[0] - '0') + (ss[1] - '0'));
  }
  return ss[0] - '0';
}

int main() {
  int n;
  cin >> n;
  vector<ll> a(n);
  rep (i, n) {
    string s;
    cin >> s;
    a[i] = digital_root(s);
  }

  ll ans = 1;
  for (auto v : a) ans *= v;

  cout << digital_root(to_string(ans)) << endl;
  
  return 0;
}