#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define s second
#define f first
#define pb push_back
#define ep emplace
#define eb emplace_back
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define uniquev(v) sort(all(v)), (v).resize(unique(all(v)) - (v).begin())
#define mem(f,x) memset(f , x , sizeof(f))
#define sz(x) (int)(x).size()
#define __lcm(a, b) (1ll * ((a) / __gcd((a), (b))) * (b))
#define mxx *max_element
#define mnn *min_element
#define cntbit(x) __builtin_popcountll(x)
#define len(x) (int)(x.length())
const int N = 1e6 + 10;
int cnt[N];
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n;
cin >> n;
int ans = 0;
for (int i = 0; i < n; i++) {
int x;
cin >> x;
if (cnt[x + 1]) {
cnt[x + 1]--;
} else {
ans++;
}
cnt[x]++;
}
cout << ans << '\n';
return 0;
}
