#include <stdio.h>
#include <string.h>
int main(){
    char binary[33];
    int i, decimal = 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 = desimal * 2 + (binary[i] - '0');
}
if (binary[0] == '1') {
    desimal = desimal - (1 << len);
}

printf("%d\n", desimal);
return 0;
}