#include <bits/stdc++.h>
using namespace std;
string to_string(string s) { return '"' + s + '"'; }
string to_string(const char *s) { return to_string((string)s); }
string to_string(bool b) { return (b ? "true" : "false"); }
template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}
template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
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); }
int base = 1;
vector<num> roots = {{0, 0}, {1, 0}};
vector<int> rev = {0, 1};
const double PI = acosl(-1.0);
void ensure_base(int nbase) {
  if (nbase <= base) {
    return;
  }
  rev.resize(1 << nbase);
  for (int 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 (int 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, int n = -1) {
  if (n == -1) {
    n = a.size();
  }
  assert((n & (n - 1)) == 0);
  int zeros = __builtin_ctz(n);
  ensure_base(zeros);
  int shift = base - zeros;
  for (int i = 0; i < n; i++) {
    if (i < (rev[i] >> shift)) {
      swap(a[i], a[rev[i] >> shift]);
    }
  }
  for (int k = 1; k < n; k <<= 1) {
    for (int i = 0; i < n; i += 2 * k) {
      for (int 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<int> multiply(vector<int> &a, vector<int> &b) {
  int need = a.size() + b.size() - 1;
  int nbase = 1;
  while ((1 << nbase) < need) nbase++;
  ensure_base(nbase);
  int sz = 1 << nbase;
  if (sz > (int)fa.size()) {
    fa.resize(sz);
  }
  for (int i = 0; i < sz; i++) {
    int x = (i < (int)a.size() ? a[i] : 0);
    int y = (i < (int)b.size() ? b[i] : 0);
    fa[i] = num(x, y);
  }
  fft(fa, sz);
  num r(0, -0.25 / (sz >> 1));
  for (int i = 0; i <= (sz >> 1); i++) {
    int 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;
  }
  for (int i = 0; i < (sz >> 1); i++) {
    num A0 = (fa[i] + fa[i + (sz >> 1)]) * num(0.5, 0);
    num A1 = (fa[i] - fa[i + (sz >> 1)]) * num(0.5, 0) * roots[(sz >> 1) + i];
    fa[i] = A0 + A1 * num(0, 1);
  }
  fft(fa, sz >> 1);
  vector<int> res(need);
  for (int i = 0; i < need; i++) {
    if (i % 2 == 0) {
      res[i] = fa[i >> 1].x + 0.5;
    } else {
      res[i] = fa[i >> 1].y + 0.5;
    }
  }
  return res;
}
vector<int> square(const vector<int> &a) {
  int need = a.size() + a.size() - 1;
  int nbase = 1;
  while ((1 << nbase) < need) nbase++;
  ensure_base(nbase);
  int sz = 1 << nbase;
  if ((sz >> 1) > (int)fa.size()) {
    fa.resize(sz >> 1);
  }
  for (int i = 0; i < (sz >> 1); i++) {
    int x = (2 * i < (int)a.size() ? a[2 * i] : 0);
    int y = (2 * i + 1 < (int)a.size() ? a[2 * i + 1] : 0);
    fa[i] = num(x, y);
  }
  fft(fa, sz >> 1);
  if ((sz >> 1) > (int)fb.size()) {
    fb.resize(sz >> 1);
  }
  num rr(1.0 / sz, 0.0);
  for (int i = 0; i < (sz >> 1); i++) {
    int j = ((sz >> 1) - i) & ((sz >> 1) - 1);
    num fbb = (fa[i] + conj(fa[j])) * num(0.5, 0);
    num fc = (fa[i] - conj(fa[j])) * num(0, -0.5);
    num new_fbb = fbb + roots[(sz >> 1) + i] * fc;
    fc = fbb - roots[(sz >> 1) + i] * fc;
    fbb = new_fbb;
    fbb = fbb * fbb * rr;
    fc = fc * fc * rr;
    num A0 = (fbb + fc);
    num A1 = (fc - fbb) * (i == 0 ? roots[(sz >> 1) + i] : roots[sz - i]);
    if (i == 0) A1 = A1 * num(-1, 0);
    fb[i] = A0 + A1 * num(0, 1);
  }
  for (int i = 0; i < (sz >> 1); i++) {
    fa[i] = fb[i];
  }
  reverse(fa.begin() + 1, fa.end());
  fft(fa, sz >> 1);
  vector<int> res(need);
  for (int i = 0; i < need; i++) {
    if (i % 2 == 0) {
      res[i] = fa[i >> 1].x + 0.5;
    } else {
      res[i] = fa[i >> 1].y + 0.5;
    }
  }
  return res;
}
vector<int> multiply_mod(vector<int> &a, vector<int> &b, int m, int eq = 0) {
  int need = a.size() + b.size() - 1;
  int nbase = 0;
  while ((1 << nbase) < need) nbase++;
  ensure_base(nbase);
  int sz = 1 << nbase;
  if (sz > (int)fa.size()) {
    fa.resize(sz);
  }
  for (int i = 0; i < (int)a.size(); i++) {
    int 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 > (int)fb.size()) {
    fb.resize(sz);
  }
  if (eq) {
    copy(fa.begin(), fa.begin() + sz, fb.begin());
  } else {
    for (int i = 0; i < (int)b.size(); i++) {
      int 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);
  num r3(ratio, 0);
  num r4(0, -ratio);
  num r5(0, 1);
  for (int i = 0; i <= (sz >> 1); i++) {
    int 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<int> res(need);
  for (int 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<int> square_mod(vector<int> &a, int m) {
  return multiply_mod(a, a, m, 1);
}
};  // namespace fft
void multiply(vector<int> &a, int b) {
  int carry = 0;
  for (int i = 0; i < (int)a.size(); i++) {
    carry += a[i] * b;
    a[i] = carry % 10;
    carry /= 10;
  }
  while (carry > 0) {
    a.push_back(carry % 10);
    carry /= 10;
  }
}
void divide(vector<int> &a, int b) {
  int md = 0;
  for (int i = (int)a.size() - 1; i >= 0; i--) {
    md = 10 * 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<int> &a, const vector<int> &b) {
  if (a.size() != b.size()) {
    return (a.size() < b.size());
  }
  for (int i = (int)a.size() - 1; i >= 0; i--) {
    if (a[i] != b[i]) {
      return (a[i] < b[i]);
    }
  }
  return false;
}
vector<int> sp3;
void get_p3(int p3) {
  if (p3 <= 0) {
    return;
  }
  if (p3 & 1) {
    get_p3(p3 - 1);
    multiply(sp3, 3);
  } else {
    get_p3(p3 >> 1);
    sp3 = fft::square(sp3);
    int carry = 0;
    for (int i = 0; i < (int)sp3.size(); i++) {
      carry += sp3[i];
      sp3[i] = carry % 10;
      carry /= 10;
    }
    while (carry > 0) {
      sp3.push_back(carry % 10);
      carry /= 10;
    }
  }
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  string foo;
  cin >> foo;
  if (foo == "1") {
    cout << 1 << '\n';
    return 0;
  }
  int len = (int)foo.size();
  vector<int> s(len);
  for (int i = 0; i < len; i++) {
    s[i] = (int)(foo[len - 1 - i] - '0');
  }
  int p3 = (int)(logl(10) * (len - 1) / logl(3));
  sp3.assign(1, 1);
  get_p3(p3);
  int ans = 3 * p3;
  while (is_less(sp3, s)) {
    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++;
  }
  cout << ans << '\n';
  return 0;
}
