#include <bits/stdc++.h>
using namespace std;
#define ll long long
const ll MOD = 1000000007;
bool check(int x,vector<int>& v,int d,int n){
bool c=true;
int p_vac=0,p_day=0;
// cout<<x<<endl;
for (int i = 1; i <= n; i++)
{
// for (int i = 0; i < n; i++)
// {
// cout<<p_day<<" ";
// }
if(!c)break;
if(p_day==0&&v[i]==0)continue;
if(p_day&&v[i]==0){
p_day--;
p_vac=0;
continue;
}
if(p_day==0){
p_day=(v[i]+x-1)/x;
if(p_day>d){
c=false;
break;
}
p_day--;
p_vac=x-v[i]%x;
if(p_vac==x)p_vac=0;
continue;
}
if(p_vac&&v[i]<=p_vac){
p_vac--;
}else{
v[i]-=p_vac;
p_day+=(v[i]+x-1)/x;
if(p_day>d){
c=false;
break;
}
p_vac=x-v[i]%x;
if(p_vac==x)p_vac=0;
}
p_day--;
}
// cout<<endl;
return c;
}
int main()
{
int n,d,m,x;
cin>>n>>d>>m;
vector<int> v(n+1,0);
for (int i = 0; i < m; i++)
{
cin>>x;
v[x]++;
}
int l=0,r=n,mid;
while(r-l>1){
mid=(l+r)/2;
if(check(mid,v,d,n)){
r=mid;
}else{
l=mid;
}
}
cout<<r<<endl;
return 0;
}
