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