#include <fstream>

using namespace std;

int v[1000001],dp[1000001],st[1000001];

int main()
{
    ifstream cin("zombie.in");
    ofstream cout("zombie.out");
    int d,n,k,i,aux=0;
    cin>>d>>n>>k;
    aux=0;
    for(i=0; i<n; i++)
    {
        cin>>v[i];
        while(v[aux]+d-1<=v[i])
            aux++;
        st[i]=aux;
    }
    dp[0]=1;
    for(i=1;i<n;i++)
      dp[i]=min(dp[i-1]+1,dp[st[i]-1]+k);
    cout<<dp[n-1];
    return 0;
}