#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main(){
ll n,d,m; cin>>n>>d>>m;
vector<vector<ll>> J(n);
for(ll i=0;i<m;i++){
ll a;cin>>a;
J[a-1].push_back(i);
}
ll l=1,r=m;
while(l<r){
ll mid=(l+r)/2;
bool able=true;
queue<pair<ll, ll>> q;
for(ll i=0;i<n;i++){
q.push({i, J[i].size()});
if(q.front().first + d < i){
able = false;
break;
}
ll diff = mid;
while(!q.empty() && diff > 0){
if(q.front().second <= diff){
diff -= q.front().second;
q.pop();
}
else{
q.front().second -= diff;
diff = 0;
}
}
}
if(q.size() != 0){
able = false;
}
if(able){
r = mid;
}
else
l = mid+1;
}
cout << l << '\n';
// queue<pair<ll, ll>> q;
// for(ll i=0;i<n;i++){
// q.push({i, J[i].size()});
// ll diff = l;
// while(!q.empty() && diff > 0){
// if(q.front().second <= diff){
// diff -= q.front().second;
// for(ll j=0;j<q.front().second;j++){
// cout << J[q.front().first].back()+1 << ' ';
// J[q.front().first].pop_back();
// }
// q.pop();
// }
// else{
// for(ll j=0;j<diff;j++){
// cout << J[q.front().first].back()+1 << ' ';
// J[q.front().first].pop_back();
// }
// q.front().second -= diff;
// diff = 0;
// }
// }
// cout << 0 << '\n';
// }
}
