题目传送门
1 /*
2 水题：求总数字个数，开long long竟然莫名其妙WA了几次，也没改啥又对了:)
3 */
4 #include <cstdio>
5 #include <iostream>
6 #include <algorithm>
7 #include <cstring>
8 #include <cmath>
9 #include <vector>
10 #include <string>
11 #include <queue>
12 #include <map>
13 #include <set>
14 using namespace std;
15
16 typedef long long ll;
17 const int MAXN = 1e2 + 10;
18 const int INF = 0x3f3f3f3f;
19
20 int main(void) //Codeforces Round #308 (Div. 2) B. Vanya and Books
21 {
22 // freopen ("B.in", "r", stdin);
23
24 ll n;
25 while (scanf ("%I64d", &n) == 1)
26 {
27 int len = 0; ll tmp = n;
28 while (tmp)
29 {
30 tmp /= 10; len++;
31 }
32
33 ll ans = 0; ll x = 9;
34 for (int i=1; i<=len-1; ++i)
35 {
36 ans += x * i; x *= 10;
37 }
38 ll y = 1;
39 for (int i=1; i<=len-1; ++i) y *= 10;
40
41 ans += (n - y + 1) * len;
42 printf ("%I64d
", ans);
43 }
44
45
46 return 0;
47 }