#include <stdio.h>
#include <stdint.h>
uint16_t binary_to_uint(const char *str) {
// Your logic here
uint16_t res = 0;
for (uint8_t i = 0; str[i] != '\0'; i++)
{
res <<= 1;
res += (str[i] - '0');
}
return res;
}
int main() {
char bin[20];
scanf("%s", bin);
printf("%u", binary_to_uint(bin));
return 0;
}