【Link】:http://codeforces.com/contest/841/problem/A

【Description】

【Solution】



模拟,贪心,每个朋友尽量地多给气球。



【NumberOf WA】

【Reviw】

【Code】

#include <bits/stdc++.h>

using namespace std;

#define lson l,m,rt<<1

#define rson m+1,r,rt<<1|1

#define LL long long

#define rep1(i,a,b) for (int i = a;i <= b;i++)

#define rep2(i,a,b) for (int i = a;i >= b;i--)

#define mp make_pair

#define pb push_back

#define fi first

#define se second

#define ms(x,y) memset(x,y,sizeof x)

#define ri(x) scanf("%d",&x)

#define rl(x) scanf("%lld",&x)

#define rs(x) scanf("%s",x+1)

#define oi(x) printf("%d",x)

#define ol(x) printf("%lld",x)

#define oc putchar(' ')

#define os(x) printf(x)

#define all(x) x.begin(),x.end()

#define Open() freopen("F:\\rush.txt","r",stdin)

#define Close() ios::sync_with_stdio(0)

typedef pair<int,int> pii;

typedef pair<LL,LL> pll;

const int dx[9] = {0,1,-1,0,0,-1,-1,1,1};

const int dy[9] = {0,0,0,-1,1,-1,1,-1,1};

const double pi = acos(-1.0);

const int N = 110;

char s[N];

int n,k,num[N];

int main(){

    //Open();

    //Close();

    ri(n),ri(k);

    rs(s);

    rep1(i,1,n){

        num[s[i]-'a'+1]++;

    }

    rep1(i,1,k){

        int cnt = 0;

        rep1(i,1,26)

            if (num[i]){

                cnt++;

                num[i]--;

            }

        n-=cnt;

    }

    if (n==0){

        puts("YES");

    }else{

        puts("NO");

    }

    return 0;

}