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