10223.cpp

/**
 *                                   ____
 *       ____ ___  ____ ________  __/ __/
 *      / __ `__ \/ __ `/ ___/ / / / /_
 *     / / / / / / /_/ / /  / /_/ / __/
 *    /_/ /_/ /_/\__,_/_/   \__,_/_/
 *
 *    @link : https://the-redback.com
 */
#include <bits/stdc++.h>
using namespace std;

#define mem(a, b) memset(a, b, sizeof(a))
#define pb        push_back
#define pp        pop_back
#define inf       1000000000
#define NN        30

long long a[25];

int main() {
    int i, j, k, l;
    int tc, t;
    int n, m;
    long long x, y, z;
    a[0] = 0;
    a[1] = 1;
    for (i = 2; i <= 20; i++) {
        x = a[i - 1] * 2 * (2 * i - 1);
        a[i] = x / (i + 1);
    }
    while (~scanf("%lld", &x)) {
        for (i = 0; i < 20; i++) {
            if (a[i] < x && x <= a[i + 1]) {
                printf("%d\n", i + 1);
                break;
            }
        }
    }
    return 0;
}