Language: C++

#include <iostream>
#include <complex>
#include <sstream>
#include <string>
#include <algorithm>
#include <deque>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <vector>
#include <set>
#include <limits>
#include <cstdio>
#include <cctype>
#include <cmath>
#include <cstring>
#include <cstdlib>
#include <ctime>
#include <climits>
#include <iomanip>
#include <stack>
#include <bitset>

#define REP(i, n) for(int i = 0; i < (int)(n); i++)
#define FOR(i, j, k) for(int i = (int)(j); i < (int)(k); ++i)
#define ROF(i, j, k) for(int i = (int)(j); i >= (int)(k); --i)
#define FORLL(i, n, m) for(long long i = n; i < (long long)(m); i++)
#define SORT(v, n) sort(v, v+n)
#define REVERSE(v) reverse((v).begin(), (v).end())

using namespace std;
using ll = long long;
const ll MOD=1000000007LL;
typedef pair<int, int> P;

ll ADD(ll x, ll y) { return (x+y) % MOD; }
ll SUB(ll x, ll y) { return (x-y+MOD) % MOD; }
ll MUL(ll x, ll y) { return x*y % MOD; }
ll POW(ll x, ll e) { ll v=1; for(; e; x=MUL(x,x), e>>=1) if (e&1) v = MUL(v,x); return v; }
ll DIV(ll x, ll y) { /*assert(y%MOD!=0);*/ return MUL(x, POW(y, MOD-2)); }

template<class T> bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a,const T &b){if(a>b){a=b;return 1;}return 0;}

int
main(void){  
  ios_base::sync_with_stdio(false);
  cin.tie(0);

  int n;
  string s;

  cin >> n;
  vector<int> h(n);
  REP(i,n) cin >> h[i];

  ll max_val = h[0];

  if(n == 1){
    cout << "Yes" << endl;
    return 0;
  }
  
  FOR(i,1,n){
    if(a[i] < max_val-1) {
      cout << "No" << endl;
      return 0;
    }
    max_val = max(max_val, h[i]);
  }
  cout << "Yes" << endl;
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:66:8: error: 'a' was not declared in this scope
   66 |     if(a[i] < max_val-1) {
      |        ^
a.cc:70:18: error: no matching function for call to 'max(ll&, __gnu_cxx::__alloc_traits<std::allocator<int>, int>::value_type&)'
   70 |     max_val = max(max_val, h[i]);
      |               ~~~^~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/string:51,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_algobase.h:257:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::max(const _Tp&, const _Tp&)'
  257 |     max(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:257:5: note:   template argument deduction/substitution failed:
a.cc:70:18: note:   deduced conflicting types for parameter 'const _Tp' ('long long int' and '__gnu_cxx::__alloc_traits<std::allocator<int>, int>::value_type' {aka 'int'})
   70 |     max_val = max(max_val, h[i]);
      |               ~~~^~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::max(const _Tp&, const _Tp&, _Compare)'
  303 |     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/algorithm:61,
                 from a.cc:5:
/usr/include/c++/14/bits/stl_algo.h:5706:5: note: candidate: 'template<class _Tp> constexpr _Tp std::max(initializer_list<_Tp>)'
 5706 |     max(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5706:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5716:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::max(initializer_list<_Tp>, _Compare)'
 5716 |     max(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5716:5: note:   template argument deduction/substitution failed:
a.cc:70:18: note:   mismatched types 'std::initializer_list<_Tp>' and 'long long int'
   70 |     max_val = max(max_val, h[i]);
      |               ~~~^~~~~~~~~~~~~~~