#include <stdio.h>
#include <stdint.h>
#include<math.h>
uint16_t binary_to_uint(const char *str) {
// Your logic here
const char *start = str;
uint16_t val=0;
int power = 0;
while(*str != '\0'){
str++;
}
str--;
while(str >= start){
if(*str == '1'){
val += pow(2,power);
}
str--;
power++;
}
return val;
}
int main() {
char bin[20];
scanf("%s", bin);
printf("%u", binary_to_uint(bin));
return 0;
}