#include <cstdio>
#define nmax 1000010

long long d[nmax];
int x, n, k, v[nmax];

int main()
{
	freopen("zombie.in","r",stdin);
	freopen("zombie.out","w",stdout);
	scanf("%d %d %d",&x, &n, &k);
	int i, p;
	for (i=1; i<=n; i++) scanf("%d", &v[i]);
	p=0;
	for (i=1; i<=n; i++)
	{
		while (v[i]-v[p]>=x) p++;
		d[i]=d[i-1]+1;
		if (p)
			if (d[p-1]+k<d[i]) d[i]=d[p-1]+k;
	}
	printf("%lld\n",d[n]);
}