#include <stdio.h>
#include <stdint.h>
uint16_t binary_to_uint(const char *str) {
int dec = 0;
while(*str){
dec = dec*2 + (*str - '0');
str++;
}
return dec;
}
int main() {
char bin[20];
scanf("%s", bin);
printf("%u", binary_to_uint(bin));
return 0;
}