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