#include <stdio.h>
#include <stdint.h>
uint16_t binary_to_uint(const char *str) {
int value = 0;
for (int i=0; str[i]; i++) {
value = (value << 1) | (str[i] - '0');
}
return value;
}
int main() {
char bin[20];
scanf("%s", bin);
printf("%u", binary_to_uint(bin));
return 0;
}