#include <iostream>
#include <bits/stdc++.h>
using namespace std;
#define int long long
void solve()
{
int n,d,m;
cin>>n>>d>>m;
vector<int> a(n,0);
vector<pair<int,int>> jobs(m);
for(int i=0;i<m;i++)
{
int x;
cin>>x;
a[x-1]++;
jobs[i] = {x-1,i+1};
}
sort(jobs.begin(),jobs.end());
auto f = [&](int x)
{
vector<int> b = vector<int>(a.begin(),a.end());
int i = 0;
int day = 0;
while(i<n)
{
if(i<=day-d-1) return false;
int tot = x;
while(i<n && tot-b[i]>=0)
{
tot = tot-b[i];
i++;
}
b[i] -= tot;
day++;
}
return true;
};
int l=1; int r=m;
int ans = -1;
while(l<=r)
{
int mid = (l+r)/2;
if(f(mid))
{
ans = mid;
r = mid-1;
}
else l=mid+1;
}
cout<<ans<<endl;
// int j = 0;
// while(j<m)
// {
// int tot = ans;
// while(j<m && tot>0)
// {
// cout<<jobs[j].second<<" ";
// tot--;
// j++;
// }
// cout<<0<<endl;
// }
return;
}
int32_t main()
{
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int T;
//cin>>T;
T = 1;
while(T--)
{
solve();
}
return 0;
}
