#include <stdio.h>
#define MAXN 1000000
int din[MAXN + 1], v[MAXN + 1];

inline int min2(int a, int b){
  return a < b ? a : b;
}

int main(){
  FILE *in = fopen("zombie.in", "r");
  int d, n, k, i, st = 1;
  fscanf(in, "%d%d%d", &d, &n, &k);
  d--;
  for(i = 1; i <= n; i++){
    fscanf(in, "%d", &v[i]);
    while(v[i] - v[st] > d)
      st++;
    din[i] = min2(din[st - 1] + k, din[i - 1] + 1);
  }
  fclose(in);
  FILE *out = fopen("zombie.out", "w");
  fprintf(out, "%d", din[n]);
  fclose(out);
  return 0;
}