#include <stdio.h>
#include <stdint.h>
#include<string.h>
uint16_t binary_to_uint(const char *str) {
int l=strlen(str);
int i,j=1,sum=0;
for(i=l-1;i>=0;i--){
if(str[i]=='1')
sum=sum+j;
j=j*2;
}
return sum;
}
int main() {
char bin[20];
scanf("%s", bin);
printf("%u", binary_to_uint(bin));
return 0;
}