#include<stdio.h>
#include<string.h>
#include<ctype.h>

int main() {
    char bin[40];
    scanf("%s", bin);
    
    int n = strlen(bin);
     for (int i = 0; i < n; i++) {
         if(bin[i] != '0' && s[i] != '1') {
             printf("Invalid Input");
             return 0;
     }
     }
     long long result = 0;
     if (bin[0] == '0') {
         for(int i = 0; i < n; i++) {
             result = (result << 1) + (bin[i] - '0');
         }
     }
     else {
         result = -(1LL << (n - 1));
         for (int i = 1; i < n; i++) {
             result += ((long long)(bin[i] - '0')) << (n - 1 - i);
         }
     }
     printf("%lld", result);
     return 0;
}