#include<iostream>
#include<cstdio>
#include<cmath>
#include<stdlib.h>
using namespace std;
int main()
{
cout<<log2(4)<<endl;
cout<<log10(1000)<<endl;
cout<<log(20)<<endl;
return 0;
}
#include<cstdio>
#include<cmath>
#include<stdlib.h>
using namespace std;
int main()
{
cout<<log2(4)<<endl;
cout<<log10(1000)<<endl;
cout<<log(20)<<endl;
return 0;
}