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