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