C++ :

#include<bits/stdc++.h>
using namespace std;
long long n,L=1,R,M;
long long check(long long x)
{
	return trunc(log(x)/log(10)*x)+1;
}
int main()
{
    cin>>n;R=n;
	while(L<=R)
	{
		M=(L+R)/2;
		if(check(M)>=n)R=M-1;
		else L=M+1;
	}    
	cout<<L;
    return 0;
}