#include <stdio.h>
#include <stdint.h>
uint16_t binary_to_uint(const char *str) {
uint16_t result=0;
int i=0;
while(str[i] != '\0'){
result = result * 2 + (str[i]-'0');
i++;
}
return result;
}
int main() {
char bin[20];
scanf("%s", bin);
printf("%u", binary_to_uint(bin));
return 0;
}