#include <stdio.h>
#include <stdint.h>
uint16_t binary_to_uint(const char *str) {
uint16_t ret_val = 0;
while(*str){
ret_val <<= 1; //multiply by 2
ret_val |= (*str == '1') ? 1 : 0 ;
str++;
}
return ret_val;
}
int main() {
char bin[20];
scanf("%s", bin);
printf("%u", binary_to_uint(bin));
return 0;
}