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