#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

#define REP(i, n) for(int i=0; i<(n); ++i)
#define FOR(i, a, b) for(int i=(a); i<(b); ++i)
#define FORR(i, a, b) for(int i=(b)-1; i>=(a); --i)

#define DEBUG(x) cout<<#x<<": "<<(x)<<'\n'
#define DEBUG_VEC(v) cout<<#v<<":";REP(i, v.size())cout<<' '<<v[i];cout<<'\n'
#define ALL(a) (a).begin(), (a).end()

template<typename T> inline void CHMAX(T& a, const T b) {if(a<b) a=b;}
template<typename T> inline void CHMIN(T& a, const T b) {if(a>b) a=b;}

constexpr ll MOD=1000000007ll;
// constexpr ll MOD=998244353ll;
#define FIX(a) ((a)%MOD+MOD)%MOD

const double EPS=1e-11;
#define EQ0(x) (abs((x))<EPS)
#define EQ(a, b) (abs((a)-(b))<EPS)

std::ostream &operator<<(std::ostream &dest, __int128_t value) {
  std::ostream::sentry s(dest);
  if (s) {
    __uint128_t tmp = value < 0 ? -value : value;
    char buffer[128];
    char *d = std::end(buffer);
    do {
      --d;
      *d = "0123456789"[tmp % 10];
      tmp /= 10;
    } while (tmp != 0);
    if (value < 0) {
      --d;
      *d = '-';
    }
    int len = std::end(buffer) - d;
    if (dest.rdbuf()->sputn(d, len) != len) {
      dest.setstate(std::ios_base::badbit);
    }
  }
  return dest;
}

__int128 parse(string &s) {
  __int128 ret = 0;
  for (int i = 0; i < s.length(); i++)
    if ('0' <= s[i] && s[i] <= '9')
      ret = 10 * ret + s[i] - '0';
  return ret;
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  // cout<<setprecision(10)<<fixed;
  int n;
  cin>>n;
  __int128 k=1;
  REP(i, n){
    string p;
    cin>>p;
    __int128 x=parse(p);
    k*=x;
  }
  while(1){
    int cnt=0;
    __int128 kk=k;
    __int128 tmp=0;
    while(kk>0){
      tmp+=kk%10;
      kk/=10;
      ++cnt;
    }
    if(cnt<=1){
      break;
    }
    k=tmp;
  }
  cout<<k<<'\n';
  return 0;
}