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