#include <bits/stdc++.h>
#define f0(i, n) for(int i=(0); i<(n); i++)
#define f1(i, n) for(int i=(1); i<=(n); i++)
using namespace std;
typedef long long ll;
const int N = 1000002;
int n, d, m, dd[N];
pair <int, int> a[N];
bool check(int x){
f1(i, n) dd[i] = 0;
bool ok = 1;
for(int i = m; i >= 1; i--){
ok = 0;
for(int j = a[i].second; j >= a[i].first; j--){
if(dd[j] < x){
dd[j]++;
ok = 1;
break;
}
}
if(!ok) return 0;
}
return 1;
}
int main(){
ios_base::sync_with_stdio(0);
cin >> n >> d >> m;
f1(i, m){
int x; cin >> x;
a[i] = make_pair(i, i + d - 1);
}
int l = 0, r = m;
sort(a + 1, a + n + 1, [&](pair <int, int> a1, pair <int, int> a2){
if(a1.second != a2.second) return a1.second < a2.second;
return a1.first < a2.first;
});
int ans = m;
while(l <= r){
int mid = (l + r)/2;
if(check(mid)) r = mid - 1, ans = mid;
else l = mid + 1;
}
cout << ans;
}
