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