#include using namespace std; using ll = long long; constexpr int INF = (int)1e9 + 1001010; constexpr ll llINF = (ll)4e18 + 22000020; const string endn = "\n"; template inline auto vector2(size_t i, size_t j, const T &init = T()) {return vector(i, vector(j, init));} const string ELEM_SEPARATION = " ", VEC_SEPARATION = endn; template istream& operator >>(istream &i, vector &A) {for(auto &I : A) {i >> I;} return i;} template ostream& operator <<(ostream &o, const vector &A) {int i=A.size(); for(auto &I : A){o << I << (--i ? ELEM_SEPARATION : "");} return o;} template ostream& operator <<(ostream &o, const vector> &A) {int i=A.size(); for(auto &I : A){o << I << (--i ? VEC_SEPARATION : "");} return o;} template vector& operator ++(vector &A, int n) {for(auto &I : A) {I++;} return A;} template vector& operator --(vector &A, int n) {for(auto &I : A) {I--;} return A;} template bool chmax(T &a, const U &b) {return ((a < b) ? (a = b, true) : false);} template bool chmin(T &a, const U &b) {return ((a > b) ? (a = b, true) : false);} ll floor(ll a, ll b){if(b < 0) a = -a, b = -b; return a >= 0 ? a/b : (a+1)/b - 1;} ll ceil (ll a, ll b){if(b < 0) a = -a, b = -b; return a > 0 ? (a-1)/b + 1 : a/b;} ll bit(unsigned long long val, unsigned long long digit){return (val >> digit) & 1;} // ================================== ここまでテンプレ ================================== int main(int argc, char *argv[]){ ios::sync_with_stdio(false); cin.tie(nullptr); string n; cin >> n; bool is_e = n.size() >= 2 && (n.front() == '1') && all_of(n.begin()+1, n.end(), [](char c){return c == '3';}); if(!is_e) cout << -1 << endl; else cout << (int)n.size()-1 << endl; return 0; }