水题,没什么可说的,判断一下最大值就好.
/* xzppp */
#include <bits/stdc++.h>
using namespace std;
#define FFF freopen("in.txt","r",stdin);freopen("out.txt","w",stdout);
#define lson MAXN,m,rt<<1
#define rson m+1,r,rt<<1|1
#define MP make_pair
#define PB push_back
typedef long long LL;
typedef unsigned long long ULL;
const int MAXN = 10000+17;
const int INF = 0x7fffffff;
const int MOD = 1e9+7;
int a[1000];
int main()
{
//FFF
int n,k;
cin>>n>>k;
int mx = 0;
for (int i = 0; i < n; ++i)
{
char temp;
cin>>temp;
a[temp]++;
mx = max(a[temp],mx);
}
if(mx<=k)
cout<<"YES"<<endl;
else
cout<<"NO"<<endl;
return 0;
}