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