#include <stdio.h>
#include <stdint.h>
uint16_t binary_to_uint(const char *str) {
// Your logic here
uint16_t value = 0;
while(*str != '\0'){
value *= 2;
if(*str == '1'){
value+=1;
}
str++;
}
return value;
}
int main() {
char bin[20];
scanf("%s", bin);
printf("%u", binary_to_uint(bin));
return 0;
}