#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>

#define MAX_KEY 50
#define MAX_MEMO 10000

typedef struct {
    char key[MAX_KEY];
    int value;
} MemoEntry;

MemoEntry memo[MAX_MEMO];
int memoSize = 0;

int min(int a, int b) { return a < b ? a : b; }
int max(int a, int b) { return a > b ? a : b; }

int findMemo(const char* key) {
    for (int i = 0; i < memoSize; i++) {
        if (strcmp(memo[i].key, key) == 0) {
            return memo[i].value;
        }
    }
    return -1;
}

void addMemo(const char* key, int value) {
    strcpy(memo[memoSize].key, key);
    memo[memoSize].value = value;
    memoSize++;
}

int helper(int start, int end) {
    if (start >= end) return 0;
    
    char key[MAX_KEY];
    sprintf(key, "%d,%d", start, end);
    
    int cached = findMemo(key);
    if (cached != -1) return cached;
    
    int minCost = INT_MAX;
    for (int guess = start; guess <= end; guess++) {
        int costIfHigher = helper(guess + 1, end);
        int costIfLower = helper(start, guess - 1);
        int worstCase = max(costIfHigher, costIfLower) + guess;
        minCost = min(minCost, worstCase);
    }
    
    addMemo(key, minCost);
    return minCost;
}

int getMoneyAmount(int n) {
    memoSize = 0;
    return helper(1, n);
}

int main() {
    int n;
    scanf("%d", &n);
    printf("%d\n", getMoneyAmount(n));
    return 0;
}