Language: C

// template version 1.12
using namespace std;
#include <iostream>
#include <bits/stdc++.h>

// varibable settings
#define infile "../test/sample-1.in"
#define int long long //{{{
const int INF=1e18;
const int MOD=1e9+7; //}}}

// define basic macro {{{
#define _overload3(_1,_2,_3,name,...) name
#define _rep(i,n) repi(i,0,n)
#define repi(i,a,b) for(int i=(int)(a);i<(int)(b);++i)
#define rep(...) _overload3(__VA_ARGS__,repi,_rep,)(__VA_ARGS__)
#define _rrep(i,n) rrepi(i,0,n)
#define rrepi(i,a,b) for(int i=(int)((b)-1);i>=(int)(a);--i)
#define rrep(...) _overload3(__VA_ARGS__,rrepi,_rrep,)(__VA_ARGS__)
#define each(i,a) for (auto&& i : a)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define pb(a) push_back(a)
#define mp(a, b) make_pair(a, b)
#define uni(x) sort(all(x));x.erase(unique(all(x)),x.end())
#define ub upper_bound
#define lb lower_bound
#define posl(A, x) (lower_bound(all(A), x)-A.begin())
#define posu(A, x) (upper_bound(all(A),x)-A.begin())
template<class T> inline void chmax(T &a, const T &b) { if((a) < (b)) (a) = (b); }
template<class T> inline void chmin(T &a, const T &b) { if((a) > (b)) (a) = (b); }

typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef long double ld;
typedef pair<int,int> pii;
typedef tuple<int,int,int> iii;

template<typename T> using PQ = priority_queue<T, vector<T>, greater<T>>;
struct Fast { Fast(){ std::cin.tie(0); ios::sync_with_stdio(false); } } fast;

#if defined(PCM) || defined(LOCAL)
  #include "lib/dump.hpp"
#else
  #define dump(...) 42
  #define dump_1d(...) 42
  #define dump_2d(...) 42
#endif
//}}}

// 隣接リストで使う辺を表す型
struct Edge {
  int to, cost;  // 辺の接続先頂点, 辺の重み
  Edge(int to, int cost) : to(to), cost(cost) {}  // コンストラクタ
};

typedef vector<vector<Edge> > AdjList;  // 隣接リストの型
AdjList graph;  // グラフの辺を格納した構造体
                // graph[v][i]は頂点vから出るi番目の辺Edge

vector<int> dist; // 最短距離

int solve(){
    
    //int H=999;
    //int W=999;
    int H=3001;
    int W=3001;
    ll a,b,x;
    ll h,w,k;cin>>h>>w>>k;
    ll ans=0;
    
    //vector<vector<ll>> v(H, vector<int>(W));
    ll v[H][W];
    rep(i,k){
        cin>>a>>b>>x;
        v[a][b]=x;
    }
    //vector<vector<vector<ll>>> dp(H, vector<vector<ll>>(W, vector<ll>(4)));
    ll dp[1000][1000][4];
    rep(x,4){
        rep(i,1000){
            rep(j,1000){
                dp[i][j][x]=0;
            }
        }
    }
    repi(i,1,h+1){
        repi(j,1,w+1){
            
            ll up_max=0;
            rep(x,4){
                if(up_max<dp[i-1][j][x])up_max=dp[i-1][j][x];
            }
            dp[i][j][0]=up_max;
            
            if(v[i][j]!=0 && dp[i][j][1]<up_max+v[i][j])dp[i][j][1]=up_max+v[i][j];
                
            if (dp[i][j][0]<dp[i][j-1][0])dp[i][j][0]=dp[i][j-1][0];
            repi(x,1,4){
                if (dp[i][j][x]<dp[i][j-1][x])dp[i][j][x]=dp[i][j-1][x];
                if (dp[i][j][x]<dp[i][j-1][x-1]+v[i][j])dp[i][j][x]=dp[i][j-1][x-1]+v[i][j];
            }
        }
    }

    rep(x,4){
        if (ans<dp[h][w][x])ans=dp[h][w][x];
    }

    
    
    cout<<ans<<endl;
    
    return 0;
}

signed main() { //{{{
#ifdef INPUT_FROM_FILE
  std::ifstream in(infile);
  std::cin.rdbuf(in.rdbuf());
#endif
  solve();
  return 0;
} //}}}


Compiler output:
main.c:2:1: error: unknown type name 'using'
    2 | using namespace std;
      | ^~~~~
main.c:2:17: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'std'
    2 | using namespace std;
      |                 ^~~
main.c:3:10: fatal error: iostream: No such file or directory
    3 | #include <iostream>
      |          ^~~~~~~~~~
compilation terminated.