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