using System;
class Program {
static void Main() {
string str = 1001;
Console.WriteLine(Integer:+ConvertClass.Convert(str));
}
}
public static class ConvertClass {
public static int Convert(string str1) {
if (str1 == )
throw new Exception(Invalid input);
int val = 0, res = 0;
for (int i = 0; i < str1.Length; i++) {
try {
val = Int32.Parse(str1[i].ToString());
if (val == 1)
res += (int)Math.Pow(2, str1.Length - 1 - i);
else if (val > 1)
throw new Exception(Invalid!);
} catch {
throw new Exception(Invalid!);
}
}
return res;
}
}