#include <bits/stdc++.h>
using namespace std;
int main() {
  string s;
  int pearls = 0, links = 0;
  cin >> s;
  for (int i = 0; i < s.size(); i++) {
    if (s[i] == '-')
      links++;
    else
      pearls++;
  }
  if (pearls == 0)
    cout << "yes" << endl;
  else if (links % pearls == 0)
    cout << "yes" << endl;
  else
    cout << "no" << endl;
  return 0;
}
