# include using namespace std; using ll = long long; using ull = unsigned long long; const double pi = acos(-1); templateconstexpr T inf() { return ::std::numeric_limits::max(); } templateconstexpr T hinf() { return inf() / 2; } template T_char TL(T_char cX) { return tolower(cX); } template T_char TU(T_char cX) { return toupper(cX); } template bool chmin(T& a,T b) { if(a > b){a = b; return true;} return false; } template bool chmax(T& a,T b) { if(a < b){a = b; return true;} return false; } template bool is_sqare(T a) { if(floor(sqrt(a)) * floor(sqrt(a)) == a){ return true; }return false; } int popcnt(unsigned long long n) { int cnt = 0; for (int i = 0; i < 64; i++)if ((n >> i) & 1)cnt++; return cnt; } int d_sum(ll n) { int ret = 0; while (n > 0) { ret += n % 10; n /= 10; }return ret; } int d_cnt(ll n) { int ret = 0; while (n > 0) { ret++; n /= 10; }return ret; } ll gcd(ll a, ll b) { if (b == 0)return a; return gcd(b, a%b); }; ll lcm(ll a, ll b) { ll g = gcd(a, b); return a / g*b; }; template using dijk = priority_queue, greater>; # define all(qpqpq) (qpqpq).begin(),(qpqpq).end() # define UNIQUE(wpwpw) sort(all((wpwpw)));(wpwpw).erase(unique(all((wpwpw))),(wpwpw).end()) # define LOWER(epepe) transform(all((epepe)),(epepe).begin(),TL) # define UPPER(rprpr) transform(all((rprpr)),(rprpr).begin(),TU) # define rep(i,upupu) for(ll i = 0, i##_len = (upupu);(i) < (i##_len);(i)++) # define reps(i,opopo) for(ll i = 1, i##_len = (opopo);(i) <= (i##_len);(i)++) # define len(x) ((int)(x).size()) # define bit(n) (1LL << (n)) # define pb push_back #ifdef LOCAL # include "_debug_print.hpp" # define debug(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__) #else # define debug(...) (static_cast(0)) #endif struct INIT{ INIT(){ std::ios::sync_with_stdio(false); std::cin.tie(0); cout << fixed << setprecision(20); } }INIT; void solve(){ string s; cin >> s; if(s == "1"){ cout << -1 << endl; return; } if(s[0] != '1'){ cout << -1 << endl; return; } for(int i = 1;i < len(s);i++){ if(s[i] != '3'){ cout << -1 << endl; return; } } cout << len(s) - 1 << endl; } int main(){ int t = 1; //cin >> t; while(t--)solve(); }