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