#include <bits/stdc++.h>
using namespace std;
int main(int argc, char* argv[]) {
  int ch[26];
  int i = 0;
  for (i = 0; i < 26; i++) {
    ch[i] = 0;
  }
  string s;
  cin >> s;
  for (i = 0; i < s.length(); i++) {
    ch[s[i] - 'a']++;
  }
  int odd = 0;
  int even = 0;
  for (i = 0; i < 26; i++) {
    if (ch[i] > 0) {
      if (ch[i] % 2 == 1) {
        odd++;
      } else {
        even++;
      }
    }
  }
  if (odd == 0) {
    cout << 1 << endl;
    return 0;
  }
  if (even == 0) {
    cout << s.length() << endl;
    return 0;
  }
  return 0;
}
