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