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

void read(),solve();

int d,n,k,i,j,stg[1000010],t[1000010];

int main()
{
	read();
	solve();
	
	return 0;
}


void read()
{
	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",&t[i]);
}

void solve()
{
	stg[1]=1;
	for(j=1,i=2;i<=n;)
	{
		if(t[i]-t[j]>=d){j++;continue;}
		stg[i]=j;i++;
	}
	t[1]=1;
	for(i=2;i<=n;i++)
	{
		t[i]=min(t[i-1]+1,t[stg[i]-1]+k);
	}
	printf("%d\n",t[n]);
}