Language: C++

#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef unsigned int uint;
typedef unsigned char uchar;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;

#define REP(i,x) for(int i=0;i<(int)(x);i++)
#define REPS(i,x) for(int i=1;i<=(int)(x);i++)
#define RREP(i,x) for(int i=((int)(x)-1);i>=0;i--)
#define RREPS(i,x) for(int i=((int)(x));i>0;i--)
#define FOR(i,c) for(__typeof((c).begin())i=(c).begin();i!=(c).end();i++)
#define RFOR(i,c) for(__typeof((c).rbegin())i=(c).rbegin();i!=(c).rend();i++)
#define ALL(container) (container).begin(), (container).end()
#define RALL(container) (container).rbegin(), (container).rend()
#define SZ(container) ((int)container.size())
#define mp(a,b) make_pair(a, b)
#define pb push_back
#define eb emplace_back
#define UNIQUE(v) v.erase( unique(v.begin(), v.end()), v.end() );
#define __builtin_popcount __builtin_popcountll

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; }
template<class T> ostream& operator<<(ostream &os, const deque<T> &t) {
    os<<"["; FOR(it,t) {if(it!=t.begin()) os<<","; os<<*it;} os<<"]"; return os;
}
template<class T> ostream& operator<<(ostream &os, const vector<T> &t) {
    os<<"["; FOR(it,t) {if(it!=t.begin()) os<<","; os<<*it;} os<<"]"; return os;
}
template<class T> ostream& operator<<(ostream &os, const set<T> &t) {
    os<<"{"; FOR(it,t) {if(it!=t.begin()) os<<","; os<<*it;} os<<"}"; return os;
}
template<class S, class T> ostream& operator<<(ostream &os, const map<S, T> &t) {
    os<<"{"; FOR(it,t) {if(it!=t.begin()) os<<","; os<<*it;} os<<"}"; return os;
}
template<class S, class T> ostream& operator<<(ostream &os, const pair<S,T> &t) { return os<<"("<<t.first<<","<<t.second<<")";}
template<class S, class T> pair<S,T> operator+(const pair<S,T> &s, const pair<S,T> &t){ return pair<S,T>(s.first+t.first, s.second+t.second);}
template<class S, class T> pair<S,T> operator-(const pair<S,T> &s, const pair<S,T> &t){ return pair<S,T>(s.first-t.first, s.second-t.second);}

const int INF = 1<<28;
const double EPS = 1e-8;
const int MOD = 1000000007;


int T, m, m, m;

ll solve(deque<ll> d) {
    deque<ll> ld, rd;
    ll sum = 0, rsum = 0, lsum = 0;
    while(d.size() > 1) {
        sum += lsum + rsum + d.front();
        rsum += d.front();
        rd.push_back(d.front()); d.pop_front();
        if (d.size() > 1) {
            sum += lsum + rsum + d.back();
            lsum += d.back();
            ld.push_back(d.back()); d.pop_back();
        }
        cout << sum << " " << lsum << " " << rsum << endl;
    }
    ll ans = sum;
    REP(i, m - 1) {
        sum -= lsum;
        sum += rsum - rd.front() * 2;
        ll x = rd.front();
        rd.pop_front();
        rd.front() += x;
        if ((ld.size() + rd.size()) % 2 == 1) {
            sum += d.back();
            lsum -= ld.back();
            rsum += d.back();
            rd.push_back(d.back());
            d.back() = ld.front();
            ld.pop_front();
        }
        ans = max(ans, sum);
    }
    return ans;
}

int main(int argc, char *argv[]){
    ios::sync_with_stdio(false);
    while(cin >> m >> m){
        deque<ll> d, revd;
        int p = 0;
        REP(i, m) {
            ll x;
            cin >> x;
            d.push_back(x - p);
            revd.push_front(x - p);
            p = x;
        }
        d.push_back(m - p);
        revd.push_front(m - p);
        cout << max(solve(d), solve(revd)) << endl;
    }
    return 0;
}


Compiler output:
a.cc:49:11: error: redefinition of 'int m'
   49 | int T, m, m, m;
      |           ^
a.cc:49:8: note: 'int m' previously declared here
   49 | int T, m, m, m;
      |        ^
a.cc:49:14: error: redefinition of 'int m'
   49 | int T, m, m, m;
      |              ^
a.cc:49:8: note: 'int m' previously declared here
   49 | int T, m, m, m;
      |        ^