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