#include<iostream> #include<cstring> #include<cmath> using namespace std; int main(){ char a[64]; cin>>a; int len=strlen(a); int sum=0; for(int i=0,j=len-1;i<len,j>=0;i++,j--){ sum+=((a[j]-'0')*pow(2,i)); } cout<<sum; return 0; }