#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <algorithm>
#include <vector>
#include <string>

using namespace std;

#define INF 1000000000

int calc_fastest(int pos, int squares[], int goal_idx, vector<int> *footpirnt)
{
    if (pos == goal_idx)
    {
        return 0;
    }

    if (any_of(footpirnt->begin(), footpirnt->end(), [pos](int x) { return x == pos; }))
    {
        return INF;
    }

    footpirnt->push_back(pos);

    int distance = squares[pos];

    int steps_when_forward = INF;
    int steps_when_backword = INF;

    if (pos + distance <= goal_idx)
    {
        printf("move forward to %d, ", pos + distance);
        steps_when_forward = 1 + calc_fastest(pos + distance, squares, goal_idx, footpirnt);
    }

    if (pos - distance >= 0)
    {
        printf("move backword to %d, ", pos - distance);
        steps_when_backword = 1 + calc_fastest(pos - distance, squares, goal_idx, footpirnt);
    }

    return min(steps_when_forward, steps_when_backword);
}

int main()
{
    int n;
    scanf("%d", &n);

    int index = 0;
    int squares[n];

    for (int max = 1; 1; max++)
    {
        for (int i = 1; i <= max; i++)
        {
            if (index + 1 > n)
                goto BREAK_LABEL;

            squares[index] = i;
            index++;
        }
    }

BREAK_LABEL:

    vector<int> footprint{};
    int fastest = 1 + calc_fastest(0, squares, n - 1, &footprint);

    if (fastest >= INF)
    {
        printf("-1");
    }
    else
    {
        printf("%d", fastest);
    }
}