int main(){

    char *s = (char*)malloc(100001);
    scanf("%s",s);
    int arr[26] = {0};
    int l = strlen(s);
    for(int i = 0; i < l; i++){
        arr[s[i]-97]++; 
    }
    int countOdd = 0;
    for(int i = 0; i < 26; i++){
        if(arr[i] % 2 == 1)
            countOdd++;
        if(countOdd > 1){
            printf("NO");
            break;
        }
        if(i == 25)
            printf("YES");
    }
    
    return 0;
}