#include <iostream>
#include <fstream>
#include <utility>

using namespace std;


struct no_solution {};

typedef long long int integer;

pair<integer, integer> xgcd(integer a, integer b) {
  if (b == 0)
    return make_pair(1, 0);
  pair<integer, integer> p = xgcd(b, a%b);
  return make_pair(p.second, p.first - (a/b)*p.second);
}

integer gcd(integer a, integer b) {
  while(b != 0) {
    integer r = a % b;
    a = b;
    b = r;
  }
  return a;
}

integer lcm(integer a, integer b) {
  return a/gcd(a, b)*b;
}

integer divide(integer a, integer b, integer m) {
  b -= b/m*m;
  if (b < 0)
    b += m;
  integer g = gcd(a, m);
  if (b%g != 0)
    throw no_solution();
  pair<integer, integer> p = xgcd(a, m);
  //cout << p.first << ',' << a << ',' << p.second << ',' << m << endl;
  assert(p.first*a + p.second*m == gcd(a, m));
  integer n = p.first * b / g;
  integer dn = m / g;
  n -= n/dn*dn;
  if (n < 0)
    n += dn;
  return n;
}


int main() {
  ifstream fin("moduloscope.in");

  int n;
  while(fin >> n && n != 0) {

    { integer a;    fin >> a; }

    integer a, b;
    a = 0;
    b = 1;
    for(int d = 2; d <= n; d++) {
      integer c;
      fin >> c;
      integer k = divide(b, c-a, d);
      integer new_a = a + b*k;
      integer new_b = lcm(b, d);
      a = new_a;
      b = new_b;
      //cout << d << ": " << a << " + " << b << "k" << endl;
    }

    cout << a << endl;
  }

  return 0;
}