Problem:
Score : 200 points

Problem Statement

You are given a string S consisting of lowercase English letters. Determine whether all the characters in S are different.

Constraints

2 ≤ |S| ≤ 26, where |S| denotes the length of S.

S consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:

S

Output

If all the characters in S are different, print yes (case-sensitive); otherwise, print no.

Sample Input 1

uncopyrightable

Sample Output 1

yes

Sample Input 2

different

Sample Output 2

no

Sample Input 3

no

Sample Output 3

yes

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <stack>
#include <queue>
#include <cctype>
#include <cmath>
#include <map>
#include <set>
#define rep(i, m, n) for(int i = m;i < n;i++)
#define repr(i, n) for(int i = n;i >= 0;i--)
#define ll long long
#define ull unsigned long long
#define push(a) push_back(a)
#define pop(a) pop_back(a)
#define debug(x) cout<<#x<<": "<<x<<endl
#define SORT(v, n) sort(v, v+n);
#define VSORT(v) sort(v.begin(), v.end());
#define INF 999999999
#define PI 3.14159265358979
using namespace std;
typedef pair<int, int> P;
typedef pair<ll, ll> LP;
typedef pair<int, P> PP;
typedef pair<ll, LP> LPP;

int dy[]={0, 0, 1, -1, 0};
int dx[]={1, -1, 0, 0, 0};

int main(){
  string s;
  bool flag=true;
  char cnt[27]={};
  cin>>s;
  rep(i,0,s.size()){
    cnt[s[i]-'a']++;
  }
  rep(i,0,27){
    if(cnt[i]!=0&&cnt[i]%2==0)flag=false;
  }
  if(flag)cout<<"yes"<<endl;
  else cout<<"no"<<endl;
}