Problem:
Score : 300 points

Problem Statement

Snuke and Raccoon have a heap of N cards. The i-th card from the top has the integer a_i written on it.

They will share these cards.
First, Snuke will take some number of cards from the top of the heap, then Raccoon will take all the remaining cards.
Here, both Snuke and Raccoon have to take at least one card.

Let the sum of the integers on Snuke's cards and Raccoon's cards be x and y, respectively.
They would like to minimize |x-y|.
Find the minimum possible value of |x-y|.

Constraints

2 \leq N \leq 2 \times 10^5

-10^{9} \leq a_i \leq 10^{9}

a_i is an integer.

Input

Input is given from Standard Input in the following format:

N
a_1 a_2 ... a_{N}

Output

Print the answer.

Sample Input 1

6
1 2 3 4 5 6

Sample Output 1

1

If Snuke takes four cards from the top, and Raccoon takes the remaining two cards, x=10, y=11, and thus |x-y|=1. This is the minimum possible value.

Sample Input 2

2
10 -10

Sample Output 2

20

Snuke can only take one card from the top, and Raccoon can only take the remaining one card. In this case, x=10, y=-10, and thus |x-y|=20.

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <set>
#include <string>
#include <iostream>
#include <vector>
#include <algorithm>
#include <stack>
#include <queue>
#include <limits>
#include <map>
#include <numeric>

#define ll long long
using namespace std;
static ll imin = std::numeric_limits<ll>::min();
static ll imax = std::numeric_limits<ll>::max();
#define rep(i, n) for(int i = 0; (i)<(n); ++(i))
#define rep1(i, n) for(int i = 1; (i)<(n); ++(i))
#define rev_rep(i, n) for(int i = (n) - 1; (i) >= 0; --(i))
#define range(a, i, b) for(int i = (a); (i) < (b); ++(i))
#define dump(x) cout << #x << ":" << x << "\n";
#define all(v) v.begin(), v.end()
#define readl(N) ll N; cin >> N
#define readlv(N, vec) vector<ll> vec(N); rep(i, N){cin >> vec[i];}
#define greater_than [](ll l, ll r){return l > r;}
template<class T1, class T2>
std::ostream& operator << (std::ostream& os, std::map<T1, T2>& mp);
template<class T1, class T2>
std::ostream& operator << (std::ostream& os, std::pair<T1, T2>& pair);
template<class T>
std::ostream& operator << (std::ostream& os, std::vector<T>& vec);
template<class T1, class T2>
std::ostream& operator << (std::ostream& os, std::pair<T1, T2>& pair){
  os << '(' << pair.first << ',' << pair.second << ')';
  return os;
}

template<class T>
std::ostream& operator << (std::ostream& os, std::vector<T>& vec){
  std::size_t n = vec.size();
  if(n == 0){
    return os;
  }
  os << " ";
  for(ll i = 0; i<n - 1; ++i){
    os << vec[i] << " ";
  }
  os << vec[n - 1];
  os << std::endl;
  return os;
}

template<class T1, class T2>
std::ostream& operator << (std::ostream& os, std::map<T1, T2>& mp){
  std::size_t n = mp.size();
  if(n == 0){
    return os;
  }
  os << " ";
  for(auto && x:mp){
    os << x << " ";
  }
  os << std::endl;
  return os;
}

template<class T>
std::ostream& operator << (std::ostream& os, std::set<T>& mp){
  std::size_t n = mp.size();
  if(n == 0){
    return os;
  }
  os << " ";
  for(auto && x:mp){
    os << x << " ";
  }
  os << std::endl;
  return os;
}

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

ll fact(ll n){
  ll res=1;
  while(n>=0){
    res*=n;
    n--;
  }
  return res;
}
    
ll pow(ll i, ll n){
  ll res=1;
  while(n>=0){
    res*=i;
    n--;
  }
  return res;
}

ll gcd(ll l, ll r){
  if(l<r){
    return gcd(r, l);
  }
  if(r == 0){
    return l;
  }
  return gcd(r, l % r);
}

ll N, M;

// bool search(ll current, ll depth){
//   // dump(current);
//   // dump(depth);
//   if(depth > 2){
//     return false;
//   }
//   if(current == N){
//     return true;
//   }
//   bool res = false;
//   rep(i, M){
//     if(current == a[i]){
//       res = res || search(b[i], depth + 1);
//     }
//   }
//   return res;
// }

#ifndef BOOST_TEST_MAIN
int main(int const argc, char const** argv){
  readl(N);
  vector<ll> a(N), l(N), r(N);
  rep(i, N){
    cin >> a[i];
  }
  l[0] = a[0];

  rep(i, N - 1){
    l[i + 1] = l[i] + a[i + 1];
  }
  
  r[N - 1] = a[N - 1];
  for(ll i = N - 1; i > 0; --i){
    r[i - 1] = r[i] + a[i - 1];
  }

  ll res = imax;
  rep(i, N - 1){
    res = min(res, abs(r[i + 1] - l[i]));
  }
  // dump(l);
  // dump(r);
  cout << res << endl;
}
#endif