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