#include <stdio.h>
#include <stdint.h>
#include <math.h>
uint16_t binary_to_uint(const char *str) {
// Your logic here
int n=0;
uint16_t sum =0;
while(*(str+n) != '\0')
{
n++;
}
int j=0;
for(int i=n-1;i>=0;i--)
{
sum += (*(str+i) - '0') * pow(2,j);
j++;
}
return sum;
}
int main() {
char bin[20];
scanf("%s", bin);
printf("%u", binary_to_uint(bin));
return 0;
}