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