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;
}215B - Olympic Medal | 1445A - Array Rearrangment |
1351A - A+B (Trial Problem) | 935B - Fafa and the Gates |
1291A - Even But Not Even | 1269A - Equation |
441A - Valera and Antique Items | 1702C - Train and Queries |
816B - Karen and Coffee | 838D - Airplane Arrangements |
148B - Escape | 847G - University Classes |
1110A - Parity | 1215B - The Number of Products |
604C - Alternative Thinking | 1204C - Anna Svyatoslav and Maps |
322A - Ciel and Dancing | 1689B - Mystic Permutation |
1711B - Party | 1702D - Not a Cheap String |
1714F - Build a Tree and That Is It | 1703F - Yet Another Problem About Pairs Satisfying an Inequality |
610A - Pasha and Stick | 1200A - Hotelier |
1091A - New Year and the Christmas Ornament | 1352B - Same Parity Summands |
1102A - Integer Sequence Dividing | 630B - Moore's Law |
1004A - Sonya and Hotels | 1680B - Robots |