#include <bits/stdc++.h>

using namespace std;

#define mp make_pair
#define pb push_back
#define fi first
#define se second

typedef int def; //default parameter for loops

#define fori(a) for(def i=0; i<(a); i++)
#define fori1(a) for(def i=1; i<=(a); i++)
#define fori_(a) for(def i=(a)-1; i>=0; i--)
#define fori1_(a) for(def i=(a); i>0; i--)
#define forii(a, b) for(def i=(a); i<(b); i++)
#define forii_(a, b) for(def i=(b)-1; i>=(a); i--)

#define forj(a) for(def j=0; j<(a); j++)
#define forj1(a) for(def j=1; j<=(a); j++)
#define forj_(a) for(def j=(a)-1; j>=0; j--)
#define forj1_(a) for(def j=(a); j>0; j--)
#define forjj(a, b) for(def j=(a); j<(b); j++)
#define forjj_(a, b) for(def j=(b)-1; j>=(a); j--)

#define fork(a) for(def k=0; k<(a); k++)
#define fork1(a) for(def k=1; k<=(a); k++)
#define fork_(a) for(def k=(a)-1; k>=0; k--)
#define fork1_(a) for(def k=(a); k>0; k--)
#define forkk(a, b) for(def k=(a); k<(b); k++)
#define forkk_(a, b) for(def k=(b)-1; k>=(a); k--)

#define forl(a) for(def l=0; l<(a); l++)
#define forl1(a) for(def l=1; l<=(a); l++)
#define forl_(a) for(def l=(a)-1; l>=0; l--)
#define forl1_(a) for(def l=(a); l>0; l--)
#define forll(a, b) for(def l=(a); l<(b); l++)
#define forll_(a, b) for(def l=(b)-1; l>=(a); l--)

#define forg(a) for(def g=0; g<(a); g++)
#define forg1(a) for(def g=1; g<=(a); g++)
#define forg_(a) for(def g=(a)-1; g>=0; g--)
#define forg1_(a) for(def g=(a); g>0; g--)
#define forgg(a, b) for(def g=(a); g<(b); g++)
#define forgg_(a, b) for(def g=(b)-1; g>=(a); g--)

#define forf(a) for(def f=0; f<(a); f++)
#define forf1(a) for(def f=1; f<=(a); f++)
#define forf_(a) for(def f=(a)-1; f>=0; f--)
#define forf1_(a) for(def f=(a); f>0; f--)
#define forff(a, b) for(def f=(a); f<(b); f++)
#define forff_(a, b) for(def f=(b)-1; f>=(a); f--)

#define forh(a) for(def h=0; h<(a); h++)
#define forh1(a) for(def h=1; h<=(a); h++)
#define forh_(a) for(def h=(a)-1; h>=0; h--)
#define forh1_(a) for(def h=(a); h>0; h--)
#define forhh(a, b) for(def h=(a); h<(b); h++)
#define forhh_(a, b) for(def h=(b)-1; h>=(a); h--)

#define fastIO ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define endl '\n'

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<pii> vpii;
typedef vector<pll> vpll;

template <typename T>
std::ostream& operator<< (std::ostream& out, const std::vector<T>& v) {
    if ( !v.empty() ) {
        std::copy (v.begin(), v.end(), std::ostream_iterator<T>(out, " "));
    }
    return out;
}
template <typename T>
std::ostream& operator<< (std::ostream& out, const std::set<T>& v) {
    if ( !v.empty() ) {
    std::copy (v.begin(), v.end(), std::ostream_iterator<T>(out, " "));
    }
    return out;
}

const int N = 2e5+10;
const ll M = 1e9+7;

ll A[N];

int main(){
    fastIO;
    int n;
    cin>>n;
    fori(n)cin>>A[i];
    ll s = 0;
    fori(n)s+=A[i];
    ll cur = 0;
    ll a = -1;
    ll b = -1;
    fori(n-1){
        cur += A[i];
        if(cur * 2 <= s)a = cur;
        else{
            b = cur;
            break;
        }
    }
    // cerr<<a<<" "<<b<<" "<<s<<endl;
    ll ans = 2020202020;
    if(a != -1){
        ans = min(ans, (ll)2*(s-a)-s);
    }
    if(b != -1){
        ans = min(ans, (ll)2*b-s);
    }
    cout<<ans;
}


Measured memory_bytes: 1920