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