#include<bits/stdc++.h>
using namespace std;
#define int long long
int b[100000005],n,m,d,ma,x;
bool find(int k,int a[]){
	if (k*n<m) return 0;
	int now=1;
	for (int i=1;i<=n;i++){
		if ((now==ma&&a[now]==0)||now>ma) return 1;
		
		if (i-now>d) return 0;
		while ((!a[now])&&now<=i) now++;
		int jjj=k;
		while (now<=i&&a[now]<=jjj){
			jjj-=a[now];
			a[now]=0;
			now++;
		}
		a[now]-=jjj;
		if (i-now>=d) return 0;
		
	}
	return 1;
}
signed main(){
	scanf("%lld%lld%lld",&n,&d,&m);	
	for (int p=1;p<=m;p++){
		scanf("%lld",&x);
		ma=max(x,ma);
		b[x]++;
	}
	int res=1;
	while (!find(res,b)) res++; 
	printf("%lld",res);
	return 0;
}

代码不是很好看 见谅