#include <stdio.h>
#include <stdint.h>
uint16_t binary_to_uint(const char *str) {
int num = 0,fact = 1,i=0;
while(str[i] != 0){
i++;
}
i-=1;
for(;i>=0;i--){
num += (str[i] - 48)*fact;
// printf("%d ",num);
fact= fact*2;
// i++;
}
return num;
}
int main() {
char bin[20];
scanf("%s", bin);
printf("%u", binary_to_uint(bin));
return 0;
}