#include <bits/stdc++.h>
using namespace std;
string s;
int o_c;
int main() {
  cin >> s;
  int l = s.length();
  for (int i = 0; i < l; i++) {
    if (s[i] == 'o') o_c++;
  }
  if (o_c == 0 || l % o_c == 0)
    cout << "yes";
  else
    cout << "no";
}
