#include<stdio.h>
#include<string.h>
#include<math.h>
int main(){
    char bin[40];
    scanf("%s",bin);
    
    for (int i = 0;i<strlen(a) ; i++) {
        if(a[i]!='0'&&a[i] ! = '1'){
            printf("Invalid Input\n");
            return 0;
            
        }
        
    }
    int len = strlen(a);
    long long b = 0;
    if(a[0] == '1') {
        b = - (long long)pow(2, len - 1);
        
    }
    for (inti=1;i<len;i++){
        if(a[i] == '1') {
            b +=(long long) pow(2, len )
            
        }
        
    }
    printf("%lld\n",b);
    return 0;
}