#include<bits/stdc++.h> using namespace std; int n,s=0; int f(int a){ int r; if(a==1) r=n; else{ r=f(a-1)*10+n; } return r; } int main(){ cin>>n; for(int i=1;i<=n;i++){ s=s+f(i); } cout<<s; return 0; } /************************************************************** Problem: 1245 User: zhuanghaoxiang Language: C++ Result: Accepted Time:8 ms Memory:2072 kb ****************************************************************/