import std.algorithm;
import std.array;
import std.conv;
import std.math;
import std.range;
import std.stdio;
import std.string;
import std.typecons;

T read(T)() { return readln.chomp.to!T; }
T[] reads(T)() { return readln.split.to!(T[]); }
alias readint = read!int;
alias readints = reads!int;

int calc(string s) {

    if (s.front != '1') return -1;
    if (s.length == 1) return -1;
    if (s[1..$].any!(e => e != '3')) return -1;

    return cast(int)s.length - 1;
}

void main() {
    string s = read!string;
    writeln(calc(s));
}