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