#include<stdio.h>
#include<string.h>
int main()
{
    char binary[33];
    int i,n,dec = 0;
    
    scanf("%s", binary);
    int len = strlen(binary);
    for (i = 0; i < len; i++) {
        if (binary[i] != '0' && binary[i] !='1') {
            printf("Invalid Input\n");
            return 0;
        }
    }    
    for (i =0; i < len; i++){
        decimal = decimal * 2 + (binary[1] - '0');
        }
    }
    if (binary[0] == '1') {
       decimal = decimal - (1 << len);
    }
    
    printf("%d\n", decimal);
    return 0;
}