#include <stdio.h>
#include <stdint.h>
uint16_t binary_to_uint(const char *str) {
int i = 0;
int len = 0;
uint16_t result = 0;
int factor=1;
while (str[i] != '\0') {
len++;
i++;
}
for (int j=len-1; j>=0; j--) {
if (str[j] == '1') {
result += factor;
}
factor *= 2;
}
return result;
}
int main() {
char bin[20];
scanf("%s", bin);
printf("%u", binary_to_uint(bin));
return 0;
}