#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define ar array
#define vo vector
#define pb push_back
#define all(x) begin(x), end(x)
#define sz(x) (ll)(x).size()
#define rep(i, a, b) for(ll i=a; i<b; i++)
#define repd(i, a, b) for(ll i=a; i>=b; i--)
int main() {
cin.tie(0)->sync_with_stdio(0);
ll n;
cin >> n;
ll h[ll(1e6)+1];
memset(h, 0, sizeof h);
vo<ll> A(n);
rep(i, 0, n)
cin >> A[i];
repd(i, n-1, 0) {
ll a=A[i];
if(h[a-1])
h[a-1]--;
h[a]++;
}
ll ans=0;
rep(i, 0, ll(1e6+1))
ans+=h[i];
cout << ans << "\n";
}
