#include <bits/stdc++.h>
using namespace std;
#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast")
#pragma GCC optimize(3)
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC target("sse3", "sse2", "sse")
#pragma GCC target("avx", "sse4", "sse4.1", "sse4.2", "ssse3")
#pragma GCC target("f16c")
#pragma GCC optimize("inline", "fast-math", "unroll-loops", \
                     "no-stack-protector")
#pragma GCC push_options
#pragma GCC pop_options
#pragma GCC reset_options
#pragma GCC optimize("O3")
const double eps = 1e-9;
const int INFMEM = 63;
const int INF = 1061109567;
const long long LINF = 4557430888798830399LL;
const double DINF = numeric_limits<double>::infinity();
const long long MOD = 1000000007;
const int dx[8] = {1, 0, -1, 0, 1, 1, -1, -1};
const int dy[8] = {0, 1, 0, -1, 1, -1, 1, -1};
const double PI = 3.141592653589793;
inline void fastll(long long &input_number) {
  input_number = 0;
  int ch = getchar_unlocked();
  int sign = 1;
  while (ch < '0' || ch > '9') {
    if (ch == '-') sign = -1;
    ch = getchar_unlocked();
  }
  while (ch >= '0' && ch <= '9') {
    input_number = (input_number << 3) + (input_number << 1) + ch - '0';
    ch = getchar_unlocked();
  }
  input_number *= sign;
}
inline void open(string a) {
  freopen((a + ".in").c_str(), "r", stdin);
  freopen((a + ".out").c_str(), "w", stdout);
}
inline void fasterios() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
}
long long n;
long long isi[150005];
bool done[150005];
int main() {
  fasterios();
  cin >> n;
  for (int i = 1; i <= n; i++) {
    long long tmp;
    cin >> tmp;
    isi[tmp]++;
  }
  for (int i = 1; i <= 150000; i++) {
    if (i != 1 && !done[i - 1] && isi[i]) {
      done[i - 1] = 1;
      isi[i]--;
    }
    if (!done[i] && isi[i]) {
      done[i] = 1;
      isi[i]--;
    }
    if (!done[i + 1] && isi[i]) {
      done[i + 1] = 1;
      isi[i]--;
    }
  }
  long long ans = 0;
  for (int i = 1; i <= 150001; i++)
    if (done[i]) ans++;
  cout << ans << '\n';
  return 0;
}
