#include <iostream>
#include <cmath>
using namespace std;
int main() {
cout << "64 的平方根是: " << sqrt(64) << "\n";
cout << "2.6 四舍五入后的整数是: " << round(2.6) << "\n";
cout << "2 的自然对数是: " <<log(2) << "\n";
return 0;
}