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