#include <cstdio>
#include <algorithm>
using namespace std;

#define MAXN 1000010

int A[MAXN],DP[MAXN];
int i,st;
int D,N,K;

int cbin(int st, int L) {
	int dr,m,rez;
	dr=L; rez=L;
	m=(st+dr)/2;
	while(st<=dr) {
		if(A[L]-A[m]+1<=D) {
			rez=min(rez,m);
			dr=m-1;
		}
		else
			st=m+1;
		m=(st+dr)/2;
	}
	return rez;
}

int main() {
	freopen("zombie.in","r",stdin);
	freopen("zombie.out","w",stdout);
	
	scanf("%d %d %d",&D,&N,&K);
	
	for(i=1;i<=N;i++)
		scanf("%d",&A[i]);
	
	st=1; DP[1]=1;
	for(i=2;i<=N;i++) {
		st=cbin(st,i);
		DP[i]=min(DP[i-1]+1,DP[st-1]+K);
	}
	printf("%d",DP[N]);
}