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