10 5 5
2 3 4 5 6
 1 1 1
1
 1000000000000000000 10 68
9818112234872670 233245257111863071 266483628625876079 375103213040049805 431982380866113633 489732004669478331 501030096787260719 541800997319766183 551892546260532408 696178619227890200
 1000000000000000000 2 1
1 1000000000000000000
 33 32 1
1 2 3 4 5 6 7 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
 101 55 10
1 3 5 7 8 9 10 16 18 21 22 23 24 25 27 30 32 35 36 37 38 39 40 43 45 47 49 50 51 52 54 57 59 61 64 66 67 68 69 70 71 72 73 80 83 86 87 88 89 90 91 92 96 97 98
 1000000000000000000 5 1000
1 1000000000 1000000000000 1000000000000000 1000000000000001
 15 15 15
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
 21 21 20
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
 45 43 2
1 2 3 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45
 107 20 13
5 9 20 25 26 30 37 45 51 58 62 73 82 87 89 90 99 101 104 106
 3 2 1
1 2
 1000000000 2 1000000000
1 1000000000
 11 7 3
2 3 4 5 6 7 11
 13 9 4
1 2 3 6 7 8 11 12 13
 1000000000000000000 2 1000000000
102306300054748096 267367244641009859
 16 7 5
2 3 4 5 6 15 16
 35 35 1
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
 1000000000000000000 20 365
31881893160049984 103938857870698567 103962228223609431 140762820261865064 175962215264653912 239086305245565642 354522451098745823 383839975876242372 443471287955807705 478923027151493682 511195154588214957 619570919279066139 677571312513476877 705864797651447277 789633853044745934 867300890280086078 883297431113041450 891736036124527038 937306858250803630 990892290394455512

2
 1
 10
 2
 32
 15
 4
 1
 2
 35
 9
 2
 1
 4
 4
 2
 4
 35
 20

#include <bits/stdc++.h>
using namespace std;
void customrun() {}
void fast() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
}
bool isprime(long long n) {
  if (n == 1) return false;
  for (long long i = 2; (long long)i * i <= n; i++) {
    if (n % i == 0) {
      return false;
    }
  }
  return true;
}
long long fib(int n) {
  long long a = 0, b = 1, c, i;
  if (n == 0) return a;
  for (i = 2; i <= n; i++) {
    c = (a + b);
    a = b;
    b = c;
  }
  return b;
}
long long gcd(long long a, long long b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
long long extendedgcd(long long a, long long b, long long &x, long long &y) {
  if (b == 0) {
    x = 1;
    y = 0;
    return a;
  }
  long long x1, y1;
  long long d = extendedgcd(b, a % b, x1, y1);
  x = y1;
  y = x1 - y1 * (a / b);
  return d;
}
long long findgrouplcm(vector<int> &arr, int n) {
  long long ans = arr[0];
  for (long long i = 1; i < n; i++) ans = (arr[i] * (ans / (gcd(arr[i], ans))));
  return ans;
}
long long powerwithmod(long long x, unsigned long long y, long long p) {
  long long res = 1;
  x = x % p;
  if (x == 0) return 0;
  while (y > 0) {
    if (y & 1) res = (res * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return res;
}
bool comp(const pair<long long, long long> &a,
          const pair<long long, long long> &b) {
  if (a.first == b.first) return a.second < b.second;
  return a.first < b.first;
}
void solve();
int main() {
  clock_t begin = clock();
  fast();
  customrun();
  long long t = 1;
  for (long long i = (1); i < (t + 1); i += (1)) {
    solve();
  }
  clock_t end = clock();
  double time_spent = (double)(end - begin) / CLOCKS_PER_SEC;
  return 0;
}
void solve() {
  long long n, m, k;
  cin >> (n) >> m >> k;
  long long arr[m];
  for (long long i = 0; i < m; i++) cin >> (arr[i]);
  long long i = 5, cnt = 0, p = 0, res = 0, l = 10, r = 10;
  while (p < m) {
    long long temp = 0;
    while (p < m and arr[p] <= i + cnt) {
      ++p;
      ++temp;
    }
    if (temp > 0)
      ++res;
    else
      i += 5;
    cnt += temp;
  }
  cout << (res);
}
