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