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