#include <stdio.h>
#include <stdint.h>
uint16_t binary_to_uint(const char *str) {
uint16_t n = 0;
while (*str)
{
n <<= 1;
n += *str - '0';
str++;
}
return n;
}
int main() {
char bin[20];
scanf("%s", bin);
printf("%u", binary_to_uint(bin));
return 0;
}