var fs = require('fs');
var length = fs.fstatSync(process.stdin.fd).size;
var buffer = Buffer.alloc(length);
var bytesRead = fs.readSync(process.stdin.fd, buffer, 0, length, 0);
var input = buffer.toString('utf8', 0, bytesRead);
var reg=/^1(3+)$/;
var r=reg.exec(input);
if (!r) console.log(-1);
else console.log(r[1].length);