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