#include <stdio.h> #include <stdlib.h> int main(void) { int N = 0; int C = 1; int Basic = 10; int Count = 0; scanf("%d", &N); for (int i = 1; i <= N; i++) { if (i / Basic) { Basic *= 10; C++; } Count += C; } printf("%d\n", Count); return 0; }