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