// Source: https://usaco.guide/general/io
#include <bits/stdc++.h>
using namespace std;
int n, d, m;
vector<pair<int, int> > v;
vector<vector<int> > schedule(n);
bool possible(int machines){
int i = 0;
int curAmt = 0;
int day = 1;
while(i < m){
curAmt++;
// cout << "day is " << day << endl;
// cout << "curAmt is " << curAmt << endl;
// cout << "i is " << curAmt << endl;
// cout << "v[i].first is " << v[i].first << endl;
// cout << endl;
if(v[i].first < day){
return 0;
}
if(curAmt == machines){
curAmt = 0;
day++;
}
i++;
}
return 1;
}
int main() {
cin >> n >> d >> m;
for(int i = 1; i <= m; i++){
int val;
cin >> val;
val += d;
v.push_back({val, i});
}
sort(v.begin(), v.end());
// cout << possible(11) << endl;
int lo = 1;
int hi = m + 10;
int ans = 0;
while(lo <= hi){
int mid = (lo + hi)/2;
// cout << "mid is " << mid << endl;
if(possible(mid)){
// cout << "worked" << endl;
hi = mid - 1;
ans = mid;
}
else{
lo = mid + 1;
}
}
// schedule[1 - 1].push_back(0);
int i = 0;
int curAmt = 0;
int day = 1;
vector<int> row;
while(i < m){
curAmt++;
// cout << "day is " << day << endl;
// cout << "curAmt is " << curAmt << endl;
// cout << "i is " << curAmt << endl;
// cout << "v[i].first is " << v[i].first << endl;
// cout << endl;
row.push_back(v[i].second);
if(curAmt == ans){
schedule.push_back(row);
row.clear();
curAmt = 0;
day++;
}
i++;
}
// cout<< schedule[0].size() << endl;
cout << ans << endl;
// for(int i = 0; i < n; i++){
// if(schedule[i].size() != 0){
// for(int j = 0; j < schedule[i].size(); j++){
// cout << schedule[i][j] << " ";
// }
// }
// cout << 0 << endl;
// }
}
