#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 < lens; i++) {
    decimal = decimal * 2 + (binary[i] - '0');
}
if (binary[0] == '1') {
    decimal = decimal - (1 << len);
}
printf("%d\n",decimal);
return 0;
}