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