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