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