#include <stdio.h>
#include <stdint.h>
#define MAX(x, y) (((x) > (y)) ? (x) : (y))
#define MIN(x, y) (((x) > (y)) ? (y) : (x))

int main()
{
    int64_t a, data;
    scanf("%lld", &a);
    int64_t tab[a];
    int64_t dist_forward[a];
    int64_t dist_backward[a];
    int64_t result[a -1];

    for(int64_t i = 0; i < a; i++)
    {
        scanf("%lld", &data);
        tab[i] = data;
    }

    int64_t sum = 0;
    dist_forward[0] = 0;
    for(int64_t i = 0; i < a; i++)
    {
        if (i == 0) {
            dist_forward[i] =0;
            continue;
        }
        sum += tab[i - 1];
        dist_forward[i] = sum;
    }

    sum = 0;
    dist_backward[0] = 0;
    for(int64_t i = a-1; i > 0; i--)
    {
        sum += tab[i];
        dist_backward[i] = sum;
    }

    int64_t x = 0;
    int64_t y = 1;
    int64_t max_dist = 0;
    int64_t curr_dist = 0;
    int64_t next_dist = 0;

    while(y != x)
    {
        //printf("%d %d\n", x, y);
        curr_dist = MIN(
            MIN(abs(dist_forward[y] - dist_forward[x]),
                abs(dist_forward[y] + dist_backward[x])),
            MIN(abs(dist_backward[y] + dist_forward[x]),
                abs(dist_backward[y] - dist_backward[x])));
        next_dist = MIN( MIN(abs(dist_forward[y + 1] - dist_forward[x]), abs(dist_forward[y + 1] + dist_backward[x])), MIN(abs(dist_backward[y + 1] + dist_forward[x]), abs(dist_backward[y + 1] - dist_backward[x])));
        //printf("Curr dist: %lld\n", curr_dist);
        //printf("Next dist: %lld\n", next_dist);
        if(y == (a - 1))
        {
            x++;
        }
        else
        {
            if( next_dist >= curr_dist)
            {
                y++;
            }
            else
            {
                x++;
            }
        }
        max_dist = MAX(max_dist, curr_dist);
    }
    //printf("\n%d %d\n", x, y);
    //printf("\nMax distance: %d\n", max_dist);
    printf("%lld", max_dist);
}