n,k = map(int,input().split())
s = input()
new = ""
for i in s:
if i not in new:
new += i
for i in new:
if s.count(i) > k:
print("NO")
exit()
print("YES")#include <bits/stdc++.h>
using namespace std;
int main() {
int n,k;
cin>>n>>k;
string s;
cin>>s;
for (int i=0;i<n;i++){
int sum=0;
for (int j=i;j<n;j++){
if (s[i]==s[j]){
sum++;
}
}
if (sum>k){
cout<<"NO";
return 0;
}
}
cout<<"YES";
return 0;
}1430C - Numbers on Whiteboard | 1697B - Promo |
208D - Prizes Prizes more Prizes | 659A - Round House |
1492C - Maximum width | 171B - Star |
1512B - Almost Rectangle | 831B - Keyboard Layouts |
814A - An abandoned sentiment from past | 268C - Beautiful Sets of Points |
1391C - Cyclic Permutations | 11A - Increasing Sequence |
1406A - Subset Mex | 1365F - Swaps Again |
50B - Choosing Symbol Pairs | 1719A - Chip Game |
454B - Little Pony and Sort by Shift | 1152A - Neko Finds Grapes |
1719B - Mathematical Circus | 1719C - Fighting Tournament |
1642A - Hard Way | 285C - Building Permutation |
1719E - Fibonacci Strings | 1696C - Fishingprince Plays With Array |
1085A - Right-Left Cipher | 1508B - Almost Sorted |
1690C - Restoring the Duration of Tasks | 1055A - Metro |
1036D - Vasya and Arrays | 1139C - Edgy Trees |