/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author aajisaka
 */

#include<bits/stdc++.h>

using namespace std;

void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

#define SPEED ios_base::sync_with_stdio(false);cin.tie(nullptr)
#define rep(i,n) for(int i=0; i<(int)(n); i++)
#define all(v) v.begin(), v.end()
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }

using ll = long long;
using P = pair<ll, ll>;

constexpr double PI = 3.14159265358979323846;
mt19937_64 engine(chrono::steady_clock::now().time_since_epoch().count());

class Result {
public:
    void solve(istream& cin, ostream& cout) {
      SPEED;
      vector<ll> a(5);
      rep(i, 5) {
        cin >> a[i];
      }
      reverse(all(a));

      // special case
      if (a[0] == 1) {
        if (a[1] == 1) {
          if (a[2] != 2) {
            cout << 2 << endl;
            return;
          }
          if (a[3] != 3) {
            cout << 3 << endl;
            return;
          }
          if (a[4] != 5) {
            cout << 4 << endl;
            return;
          }
          cout << 5 << endl;
          return;
        } else if (a[1] == 2) {
          if (a[2] != 3) {
            cout << 2 << endl;
            return;
          }
          if (a[3] != 5) {
            cout << 3 << endl;
            return;
          }
          if (a[4] != 8) {
            cout << 4 << endl;
            return;
          }
          cout << 5 << endl;
          return;
        } else {
          cout << 1 << endl;
          return;
        }
      }

      ll now = 2;
      ll before = 1;
      while(now < a[0]) {
        now += before;
        before = now-before;
      }
      if (now == a[0]) {
        now += before;
        before = now-before;
        if (now != a[1]) {
          cout << 1 << endl;
          return;
        }
        now += before;
        before = now-before;
        if (now != a[2]) {
          cout << 2 << endl;
          return;
        }
        now += before;
        before = now-before;
        if (now != a[3]) {
          cout << 3 << endl;
          return;
        }
        now += before;
        before = now-before;
        if (now != a[4]) {
          cout << 4 << endl;
          return;
        }
        cout << 5 << endl;
        return;



      } else {
        cout << 0 << endl;
        return;
      }

    }
};

signed main() {
  Result solver;
  std::istream& in(std::cin);
  std::ostream& out(std::cout);
  solver.solve(in, out);
  return 0;
}