#include <fstream>
using namespace std;int n,i,d,k,a[1000001],st,dp[1000001];ifstream fi("zombie.in");ofstream fo("zombie.out");int main(){fi>>d>>n>>k;for(i=1;i<=n;i++)fi>>a[i];st=1;dp[1]=1;for(i=2;i<=n;i++){while(a[i]-a[st]>d)st++;dp[i]=min(dp[i-1]+1,dp[st-1]+k);}fo<<dp[n];}