#include <bits/stdc++.h>
#include <iostream>
#include <cmath>
#include <iomanip>
#include <vector>
#include <map>
#include <stack>
#include <queue>
#include <set>
using namespace std;
#define ll long long
#define pb push_back
#define el '\n'
#define mpair make_pair
#define MASK(i) (1LL << (i))
#define BIT(mask, i) (((mask) >> (i)) & 1)
#define fi first
#define se second
/* Author: Pham Gia Phuoc */
const ll MOD = 998244353;
template <class T1, class T2>
void add(T1 &a, T2 b){
a += b;
if(a >= MOD) a -= MOD;
}
template <class T1, class T2>
void sub(T1 &a, T2 b){
a -= b;
if(a < 0) a += MOD;
}
template <class T1, class T2>
bool minimize(T1 &a, T2 b){
if(a > b){a = b; return true;} return false;
}
template <class T1, class T2>
bool maximize(T1 &a, T2 b){
if(a < b){a = b; return true;} return false;
}
/** END OF TEMPLATE. DRINK A CUP OF COFFEE BEFORE READING MY CODE **/
const int MAX = 1000010;
const ll INF = (ll) 1e18 + 67LL;
const int oo = (int)(1e9 + 7);
const int NUM_BIT = 62;
#define FOR(i, a, b) for(int i = a; i <= b; i++)
#define FORD(i, a, b) for(int i = a; i >= b; i--)
int n, h[MAX];
void init(){
cin >> n;
FOR(i, 1, n) cin >> h[i];
}
int cnt[MAX];
int solve(int n, int h[]){
int ans = 0;
FOR(i, 1, n){
if(cnt[h[i] + 1] == 0){
ans++;
}
else cnt[h[i] + 1]--;
cnt[h[i]]++;
}
return ans;
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define test "test"
// freopen(test".inp", "r", stdin);
// freopen(test".out", "w", stdout);
srand(time(0));
int t = 1;
while(t--){
init();
cout << solve(n, h);
}
return 0;
}
/*** ROAD TO VOI 2025 ***/
