//In His Name
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define int ll
typedef pair<int, int> pii;
typedef pair<long long, int> pli;
typedef pair<long long, long long> pll;
#define F first
#define S second
#define pb push_back
#define bug(x) cout << "Ah shit , here we go again : " << x <<endl
#define all(x) x.begin() , x.end()
#define ceil(x,y) x/y + min(1ll,x%y)
const int maxn = 5e3 + 10, MOD = 1e9 + 7;
const ll INF = 1e18;
int n , d , m;
vector<int> v;
bool check(int mid){
multiset<int> s;
for(int i : v) s.insert(i);
int cnt = 1;
while(s.size()){
for(int i = 1 ; i <= d ; i++){
if(cnt - *s.begin() > d) return true;
if(*s.begin() <= cnt) s.erase(s.begin());
else break;
}
cnt++;
}
return false;
}
signed main(){
ios_base::sync_with_stdio(false);
cin >> n >> d >> m;
for(int i = 1 ; i <= m ; i++){
int x;
cin >> x;
v.pb(x);
}
int l = 1 , r = 1e9;
while(r - l > 1){
int mid = (l+r) >> 1;
if(check(mid)) l = mid;
else r = mid;
}
cout << r;
}
