#include<bits/stdc++.h>
using namespace std;
#define int long long
const int inf = 2000000000000000000;
signed main(){
    string s;cin>>s;
    int ans=0;
    int c=0;
    int k=0;
    for(int i=0;i<s.size();i++){
        if(i!=s.size()-1 &&  s[i]=='1'&&s[i+1]=='1'){
            k++;
        }else if(s[i]=='0'){
            ans+=k;
        }
    }
    cout<<ans<<"\n";
}