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