Language: C++

/// *********** Coded by Olium_MdioxideN ***********

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define llu unsigned long long
#define eb emplace_back
#define pb push_back
#define mp make_pair
#define ext exit(0)
#define fast ios_base :: sync_with_stdio(0), cin.tie(0), cout.tie(0)
#define newl printf("\n")
#define nl '\n'
#define endl '\n'
#define sci(x) scanf("%d",&(x))
#define scll(x) scanf("%lld",&(x))
#define sci2(x,y) scanf("%d %d",&(x),&(y))
#define pr printf
#define forr(i,b,e) for(int (i)=(b); (i) <= (e); (i)++)
#define forrv(i,b,e) for(int (i)=(b); (i) >= (e); (i)--)
#define fors(i,x) for(auto (i)=(x).begin(); (i) != (x).end(); (i)++)
#define F first
#define S second
#define mset0(x) memset((x), 0, sizeof((x)));
#define mset1(x) memset((x), -1, sizeof((x)));
#define bs binary_search
#define all(x) (x).begin(),(x).end()
#define pqmin(x) priority_queue<x, vector<x>, greater<x> >
#define pqmax(x) priority_queue<x>
#define sortd(x) sort(all(x)); reverse(all(x));
#define vi vector<int>
#define pii pair<int,int>
#define mpii map<int,int>
#define elif else if
#define pi 3.14159265358979323846D
#define gcd(x,y) __gcd(x,y)
#define lcm(x,y) __lcm(x,y)
#define runtime() cerr << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n"
#define Int inputInt()        //new int input
#define Long inputLong()      //new long input
#define Double inputDouble()  //new double input
#define String inputString()  //new string input
inline int inputInt() { int tmp; scanf(" %d", &tmp); return tmp; }
inline ll inputLong() { ll tmp; scanf(" %lld", &tmp); return tmp; }
inline double inputDouble() { double tmp; scanf(" %lf", &tmp); return tmp; }
inline string inputString() { char tmpStr[1000010]; scanf(" %s", tmpStr); return tmpStr; }
template <typename type> inline type __lcm(type n1,type n2){ return n1*(n2/gcd(n1,n2)); }
ll pow_mod(ll nn, ll pp, ll mm) { ll res = 1; while(pp > 0) { if(pp&1) res = (res * nn) % mm; pp = pp >> 1; nn = (nn * nn) % mm; } return res; }

#ifndef ONLINE_JUDGE
vector<string>vec_spltr(string s){s+=',';vector<string>res;while(!s.empty())
res.push_back(s.substr(0, s.find(','))),s=s.substr(s.find(',')+1);return res;}
void dbg_out(vector<string>__attribute__((unused))args,__attribute__((unused))int idx,
__attribute__((unused))int LINE_NUM){cerr<<endl;}template<typename Head,typename... Tail>
void dbg_out ( vector <string> args, int idx, int LINE_NUM, Head H, Tail... T)
{if(idx>0)cerr<<", ";else cerr << "Line(" << LINE_NUM << ") ";stringstream ss;ss<<H;
cerr<<args[idx]<<" = "<<ss.str();dbg_out(args,idx+1,LINE_NUM, T...);}
#define debug(...) dbg_out(vec_spltr(#__VA_ARGS__), 0, __LINE__, __VA_ARGS__)
#define in_file freopen("input.txt", "r", stdin)
#define out_file freopen("output.txt", "w", stdout)
#else
#define debug(...) 0
#define in_file 0
#define out_file 0
#endif

class stdout_cus
{
    short float_prec = 7;
public:
    inline stdout_cus operator<<(const int& arg){ printf("%d",arg); return *this; }
    inline stdout_cus operator<<(const short& arg){ printf("%d",arg); return *this; }
    inline stdout_cus operator<<(const bool& arg){ printf("%d",arg); return *this; }
    inline stdout_cus operator<<(const unsigned int& arg){ printf("%u",arg); return *this; }
    inline stdout_cus operator<<(const unsigned short& arg){ printf("%u",arg); return *this; }
    inline stdout_cus operator<<(const long long& arg){ printf("%lld",arg); return *this; }
    inline stdout_cus operator<<(const unsigned long long& arg){ printf("%llu",arg); return *this; }
    inline stdout_cus operator<<(const double& arg){ printf("%.*f",float_prec,arg); return *this; }
    inline stdout_cus operator<<(const float& arg){ printf("%.*f",float_prec,arg); return *this; }
    inline stdout_cus operator<<(const char& arg){ printf("%c",arg); return *this; }
    inline stdout_cus operator<<(const unsigned char& arg){ printf("%c",arg); return *this; }
    inline stdout_cus operator<<(const char* arg){ printf("%s",arg); return *this; }
    inline stdout_cus operator<<(const std::string& arg){ printf("%s",arg.c_str()); return *this; }
    inline stdout_cus operator<<(const stdout_cus&){ return *this; }
    inline void ignore() { fflush(stdout); }
    inline stdout_cus precision(short prec) { float_prec = prec; return *this; }
}cout_cus;
class stdin_cus
{
public:
    inline stdin_cus operator>>(const int& arg){ scanf(" %d",&arg); return *this; }
    inline stdin_cus operator>>(const short& arg){ scanf(" %d",&arg); return *this; }
    inline stdin_cus operator>>(const bool& arg){ scanf(" %d",&arg); return *this; }
    inline stdin_cus operator>>(const unsigned int& arg){ scanf(" %u",&arg); return *this; }
    inline stdin_cus operator>>(const unsigned short& arg){ scanf(" %u",&arg); return *this; }
    inline stdin_cus operator>>(const long long& arg){ scanf(" %lld",&arg); return *this; }
    inline stdin_cus operator>>(const unsigned long long& arg){ scanf(" %llu",&arg); return *this; }
    inline stdin_cus operator>>(const double& arg){ scanf(" %lf",&arg); return *this; }
    inline stdin_cus operator>>(const float& arg){ scanf(" %f",&arg); return *this; }
    inline stdin_cus operator>>(const char& arg){ scanf(" %c",&arg); return *this; }
    inline stdin_cus operator>>(const unsigned char& arg){ scanf(" %c",&arg); return *this; }
    inline stdin_cus operator>>(const char* arg){ scanf(" %s",arg); return *this; }
    inline stdin_cus operator>>(std::string& arg){ char tmp[1000000]; scanf(" %s",tmp); arg = tmp; return *this; }
    inline void ignore() { fflush(stdin); }
}cin_cus;
#define cout cout_cus
#define cin cin_cus
#define setprecision cout_cus.precision

/// * * *    Main Code Starts Now    * * *

#define MOD 10000007
#define MAX 100010
void olium();
int main()
{
    //in_file;
    //out_file;
    int t = 1;
    //cin >> t;
    forr(i,1,t)
    {
        //cout << "Case " << i << ": ";
        olium();
    }
    return 0;
}

int n;
ll a[n+1];
ll dp[100009];
ll sol(int idx)
{
    if(idx > n) return INT_MAX;
    if(dp[idx] != -1) return dp[idx];
    return dp[idx] = min(a[idx+1] + sol(idx+1), a[idx+2] + sol(idx+2));
}

void olium()
{
    mset1(dp);
    cin >> n;
    forr(i,1,n)
    {
        cin >> a[i];
    }
    cout << sol(1) << nl;
}


Compiler output:
a.cc:130:7: error: size of array 'a' is not an integral constant-expression
  130 | ll a[n+1];
      |      ~^~