#!/usr/bin/env python3
import sys

def expand(dense):
    fs = []
    for i in range(len(dense)):
        if i % 2 == 0:
            for j in range(int(dense[i])):
                fs.append(i // 2)
        else:
            for j in range(int(dense[i])):
                fs.append(None)
    return fs

def pprint(fs):
    for c in fs:
        if c is not None:
            print(c, end="")
        else:
            print(".", end="")
    print("")

def compact(fs):
    comp = [c for c in fs]
    l = 0
    r = len(fs) - 1
    while l < r:
        while comp[l] is not None:
            l += 1
        while comp[r] is None:
            r -= 1
        if l < r:
            comp[l] = comp[r]
            comp[r] = None
        l += 1
        r -= 1

    return comp

def chksum(fs):
    tot = 0
    for i in range(len(fs)):
        if fs[i] is None:
            break
        tot += fs[i] * i
    
    return tot

if __name__ == '__main__':
    dense = next(sys.stdin).strip()
    fs = expand(dense)
    comp = compact(fs)
    #pprint(fs)
    #pprint(compact(fs))
    print(chksum(comp))