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