#include <bits/stdc++.h>
#define input "zombie.in"
#define output "zombie.out"
using namespace std;
int d,n,k,a,pos,r,cost;
vector<int> v;
int main()
{
    ifstream in(input);
    ofstream out(output);
    ios_base::sync_with_stdio(false);
    in.tie(0),out.tie(0);
    in>>d>>n>>k;
    for(int i=0;i<n;++i)
        in>>a,v.push_back(a);
    while(pos<n)
    {
        r=lower_bound(v.begin()+pos+1,v.end(),v[pos]+d)-v.begin();
        --r;
        if(r>pos and r-pos+1>=k)
            cost+=k,pos=r+1;
        else ++cost,++pos;
    }
    out<<cost;
    return 0;
}