#include <stdio.h>
#include <stdint.h>
uint16_t binary_to_uint(const char *str) {
// Your logic here
uint16_t res = 0x00;
while(*str != '\0')
{
res <<= 1;
if(*str == '1') res |= 0x01;
str++;
}
return res;
}
int main() {
char bin[20];
scanf("%s", bin);
printf("%u", binary_to_uint(bin));
return 0;
}