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#include "bits/stdc++.h"
// @JASPER'S BOILERPLATE
using namespace std;
using ll = long long;
#define FOR(i, a, b) for(int i = a; i <= b; i++)
#define FORD(i, a, b) for(int i = a; i >= b; i--)
#define REP(i, b) for(int i = 0; i < b; i++)
#define PER(i, b) for(int i = b - 1; i >= 0; i--)
#define fi first
#define se second
#ifdef JASPER2
#include "debug.h"
#else
#define debug(...) 166
#endif

using pii = pair < int, int >;
const int INF = 1e9;
const int MOD = 1e9 + 7;
const int N = 1e6 + 5;

int n;
string s;
map <char, int> cnt;
void run_case() {   
    cin >> s;
    n = s.size();

    // So lan xuat hien nhieu nhat
    int c = 0;
    for (auto x : s) {
        cnt[x]++;
        c = max(c, cnt[x]);
    }
    cout << (2 * c - 1 <= n? "YES\n" : "NO\n") << "\n";
}

signed main() {
    cin.tie(0) -> sync_with_stdio(0);
    #ifdef JASPER2
        freopen("in1", "r", stdin);
    #endif

    int Test = 1;
    //cin >> Test;
    for (int test = 1; test <= Test; test++){

        run_case();
    }
}