>>440
#include<stdio.h>
#include<stdlib.h>

int main(void){
char buf[256];
long number=0L;
int i;

scanf("%s", buf);
for(i=0;buf[i]!='\0';i++){
if(buf[i]!='0' && buf[i]!='1'){
fprintf(stderr, "%s not binary.\n", buf);
exit(1);
}
number=(number<<1)|(buf[i]=='1');
}
printf("%ld\n", number);

return 0;
}