#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int u, v; ll w; };

ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

int main() {
    string s;
    while (cin >> s) {
        char c = 'a';
        vector<int> a(26);
        for (int i = 0; i < s.length(); i++) {
            int j = s[i] - 'a';
            if (!a[j]) a[j] = c++;
            s[i] = a[j];
        }
        if (s == "abc" || s == "aabbcc" || s == "aaabbbccc")
            cout << "YES" << endl;
        else
            cout << "NO" << endl;
    }
}