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