#include <stdio.h>
#include <stdint.h>
#define BASE 2
uint16_t binary_to_uint(const char *str) {
// Your logic here
uint16_t num = 0;
uint8_t len = 0;
while(str[len] != '\0'){
len++;
}
for(int i = 0;i<len;i++){
num = num*BASE+(str[i]-'0');
}
return num;
}
int main() {
char bin[20];
scanf("%s", bin);
printf("%u", binary_to_uint(bin));
return 0;
}