#include <bits/stdc++.h>
#pragma GCC optimize(3)
using namespace std;
const double PI = acos(-1.0);
namespace fft {
struct num {
  double x, y;
  num() { x = y = 0; }
  num(double x, double y) : x(x), y(y) {}
};
inline num operator+(num a, num b) { return num(a.x + b.x, a.y + b.y); }
inline num operator-(num a, num b) { return num(a.x - b.x, a.y - b.y); }
inline num operator*(num a, num b) {
  return num(a.x * b.x - a.y * b.y, a.x * b.y + a.y * b.x);
}
inline num conj(num a) { return num(a.x, -a.y); }
long long base = 1;
vector<num> roots = {{0, 0}, {1, 0}};
vector<long long> rev = {0, 1};
const double PI = acosl(-1.0);
void ensure_base(long long nbase) {
  if (nbase <= base) return;
  rev.resize(1 << nbase);
  for (long long i = 0; i < (1 << nbase); i++)
    rev[i] = (rev[i >> 1] >> 1) + ((i & 1) << (nbase - 1));
  roots.resize(1 << nbase);
  while (base < nbase) {
    double angle = 2 * PI / (1 << (base + 1));
    for (long long i = 1 << (base - 1); i < (1 << base); i++) {
      roots[i << 1] = roots[i];
      double angle_i = angle * (2 * i + 1 - (1 << base));
      roots[(i << 1) + 1] = num(cos(angle_i), sin(angle_i));
    }
    base++;
  }
}
void fft(vector<num> &a, long long n = -1) {
  if (n == -1) n = a.size();
  assert((n & (n - 1)) == 0);
  long long zeros = __builtin_ctz(n);
  ensure_base(zeros);
  long long shift = base - zeros;
  for (long long i = 0; i < n; i++)
    if (i < (rev[i] >> shift)) swap(a[i], a[rev[i] >> shift]);
  for (long long k = 1; k < n; k <<= 1) {
    for (long long i = 0; i < n; i += 2 * k) {
      for (long long j = 0; j < k; j++) {
        num z = a[i + j + k] * roots[j + k];
        a[i + j + k] = a[i + j] - z;
        a[i + j] = a[i + j] + z;
      }
    }
  }
}
vector<num> fa, fb;
vector<long long> multiply(vector<long long> &a, vector<long long> &b) {
  long long need = a.size() + b.size() - 1;
  long long nbase = 0;
  while ((1 << nbase) < need) nbase++;
  ensure_base(nbase);
  long long sz = 1 << nbase;
  if (sz > (long long)fa.size()) fa.resize(sz);
  for (long long i = 0; i < sz; i++) {
    long long x = (i < (long long)a.size() ? a[i] : 0);
    long long y = (i < (long long)b.size() ? b[i] : 0);
    fa[i] = num(x, y);
  }
  fft(fa, sz);
  num r(0, -0.25 / sz);
  for (long long i = 0; i <= (sz >> 1); i++) {
    long long j = (sz - i) & (sz - 1);
    num z = (fa[j] * fa[j] - conj(fa[i] * fa[i])) * r;
    if (i != j) fa[j] = (fa[i] * fa[i] - conj(fa[j] * fa[j])) * r;
    fa[i] = z;
  }
  fft(fa, sz);
  vector<long long> res(need);
  for (long long i = 0; i < need; i++) res[i] = fa[i].x + 0.5;
  return res;
}
vector<long long> multiply_mod(vector<long long> &a, vector<long long> &b,
                               long long m, long long eq = 0) {
  long long need = a.size() + b.size() - 1;
  long long nbase = 0;
  while ((1 << nbase) < need) nbase++;
  ensure_base(nbase);
  long long sz = 1 << nbase;
  if (sz > (long long)fa.size()) fa.resize(sz);
  for (long long i = 0; i < (long long)a.size(); i++) {
    long long x = (a[i] % m + m) % m;
    fa[i] = num(x & ((1 << 15) - 1), x >> 15);
  }
  fill(fa.begin() + a.size(), fa.begin() + sz, num{0, 0});
  fft(fa, sz);
  if (sz > (long long)fb.size()) fb.resize(sz);
  if (eq)
    copy(fa.begin(), fa.begin() + sz, fb.begin());
  else {
    for (long long i = 0; i < (long long)b.size(); i++) {
      long long x = (b[i] % m + m) % m;
      fb[i] = num(x & ((1 << 15) - 1), x >> 15);
    }
    fill(fb.begin() + b.size(), fb.begin() + sz, num{0, 0});
    fft(fb, sz);
  }
  double ratio = 0.25 / sz;
  num r2(0, -1), r3(ratio, 0), r4(0, -ratio), r5(0, 1);
  for (long long i = 0; i <= (sz >> 1); i++) {
    long long j = (sz - i) & (sz - 1);
    num a1 = (fa[i] + conj(fa[j]));
    num a2 = (fa[i] - conj(fa[j])) * r2;
    num b1 = (fb[i] + conj(fb[j])) * r3;
    num b2 = (fb[i] - conj(fb[j])) * r4;
    if (i != j) {
      num c1 = (fa[j] + conj(fa[i]));
      num c2 = (fa[j] - conj(fa[i])) * r2;
      num d1 = (fb[j] + conj(fb[i])) * r3;
      num d2 = (fb[j] - conj(fb[i])) * r4;
      fa[i] = c1 * d1 + c2 * d2 * r5;
      fb[i] = c1 * d2 + c2 * d1;
    }
    fa[j] = a1 * b1 + a2 * b2 * r5;
    fb[j] = a1 * b2 + a2 * b1;
  }
  fft(fa, sz);
  fft(fb, sz);
  vector<long long> res(need);
  for (long long i = 0; i < need; i++) {
    long long aa = fa[i].x + 0.5;
    long long bb = fb[i].x + 0.5;
    long long cc = fa[i].y + 0.5;
    res[i] = (aa + ((bb % m) << 15) + ((cc % m) << 30)) % m;
  }
  return res;
}
vector<long long> square_mod(vector<long long> &a, long long m) {
  return multiply_mod(a, a, m, 1);
}
};  // namespace fft
void multiply(vector<long long> &a, long long b) {
  long long carry = 0;
  for (long long i = 0; i < (long long)a.size(); i++) {
    carry += a[i] * b;
    a[i] = carry % 1000;
    carry /= 1000;
  }
  while (carry > 0) {
    a.push_back(carry % 1000);
    carry /= 1000;
  }
}
void divide(vector<long long> &a, long long b) {
  long long md = 0;
  for (long long i = (long long)a.size() - 1; i >= 0; i--) {
    md = 1000 * md + a[i];
    a[i] = md / b;
    md %= b;
  }
  assert(md == 0);
  while (!a.empty() && a.back() == 0) {
    a.pop_back();
  }
}
bool is_less(const vector<long long> &a, const vector<long long> &b) {
  if (a.size() != b.size()) return a.size() < b.size();
  for (long long i = (long long)a.size() - 1; i >= 0; i--)
    if (a[i] != b[i]) return a[i] < b[i];
  return false;
}
vector<long long> sp3;
void get_p3(long long p3) {
  if (p3 <= 0) return;
  if (p3 & 1) {
    get_p3(p3 - 1);
    multiply(sp3, 3);
  } else {
    get_p3(p3 >> 1);
    sp3 = fft::multiply(sp3, sp3);
    long long carry = 0;
    for (long long i = 0; i < (long long)sp3.size(); i++) {
      carry += sp3[i];
      sp3[i] = carry % 1000;
      carry /= 1000;
    }
    while (carry > 0) {
      sp3.push_back(carry % 1000);
      carry /= 1000;
    }
  }
}
string str;
int main() {
  cin >> str;
  if (str == "1") {
    puts("1");
    return 0;
  }
  long long len = (long long)str.size();
  vector<long long> v;
  long long carry = 0, cnt = 0, d = 1;
  for (long long i = len - 1; i >= 0; i--) {
    cnt++;
    carry += (long long)(str[i] - '0') * d;
    d *= 10;
    if (cnt % 3 == 0 || i == 0) {
      v.push_back(carry);
      carry = 0;
      d = 1;
    }
  }
  long long p3 = (long long)(logl(10) * (len - 1) / logl(3));
  sp3.assign(1, 1);
  get_p3(p3);
  long long ans = 3 * p3;
  while (is_less(sp3, v)) {
    if (ans <= 3)
      sp3[0] = ans + 1;
    else {
      if (ans % 3 == 0) {
        divide(sp3, 3);
        multiply(sp3, 4);
      } else {
        divide(sp3, 2);
        multiply(sp3, 3);
      }
    }
    ans++;
  }
  printf("%I64d\n", ans);
  return 0;
}
