def main():
    n = int(input())

    # n/k - n/(k+1) < 1 のとき
    # k(k+1) > n
    left, right = 1, n
    while right - left > 1:
        mid = left + (right - left) // 2
        if mid * (mid + 1) > n:
            right = mid
        else:
            left = mid
    k0 = right - 1

    ans = k0 + n // (k0 + 1)
    print(ans)


if __name__ == "__main__":
    main()