import java.util.*;
import java.io.*;

public class Main {

	void solve (FastScanner in, PrintWriter out) {
		
		String s = in.next();
		
		if (s.charAt(0) != '1') {
			out.println(-1);
			return;
		}
		
		for (int i=1; i<s.length(); i++) {
			if (s.charAt(i) != '3') {
				out.println(-1);
				return;
			}
		}
		
		if (s.length() <= 1) {
			out.println(-1);
			return;
		}
		
		out.println(s.length()-1);
		
		
		
	}



	public static void main(String[] args) {
		FastScanner in = new FastScanner(System.in);
		PrintWriter out = new PrintWriter(System.out);
		Main main = new Main();
		main.solve(in, out);
		in.close();
		out.close();
	}

	static class FastScanner {

		private InputStream in;
		private byte[] buffer = new byte[1024];
		private  int length = 0, p = 0;

		public FastScanner (InputStream stream) {
			in = stream;
		}
		public boolean hasNextByte () {
			if (p < length) return true;
			else {
				p = 0;
				try {length = in.read(buffer);}
				catch (Exception e) {e.printStackTrace();}
				if (length <= 0) return false;
			}
			return true;
		}
		public int readByte () {
			if (hasNextByte() == true) return buffer[p++];
			return -1;
		}
		public boolean isPrintable (int n) {return 33<=n&&n<=126;}
		public void skip () {
			while (hasNextByte() && !isPrintable(buffer[p])) p++;
		}
		public boolean hasNext () {skip(); return hasNextByte();}
		public String next () {
			if (!hasNext()) throw new NoSuchElementException();
			StringBuilder sb = new StringBuilder();
			int t = readByte();
			while (isPrintable(t)) {
				sb.appendCodePoint(t);
				t = readByte();
			}
			return sb.toString();
		}
		public int nextInt () {return Math.toIntExact(nextLong());}
		public int[] nextIntArray (int n) {
			int[] ar = new int[n];
			for (int i=0; i<n; i++) ar[i] = nextInt();
			return ar;
		}
		public long nextLong () {
			if (!hasNext()) throw new NoSuchElementException();
			boolean minus = false;
			int temp = readByte();
			if (temp == '-') {
				minus = true;
				temp = readByte();
			}
			if (temp<'0' || '9'<temp) throw new NumberFormatException();
			long n = 0;
			while (isPrintable(temp)) {
				if ('0'<=temp && temp<='9') {
					n *= 10;
					n += temp - '0';
				}
				else throw new NumberFormatException();
				temp = readByte();
			}
			return minus? -n : n;
		}
		public double nextDouble () {
			return Double.parseDouble(next());
		}
		public void close () {
			try {in.close();}
			catch(Exception e){}
		}
	}

}