3.4

#include<iostream>

int main()
{
using namespace std;

const int Minute_to_second = 60;//1分钟=60秒；
const int Hour_to_minute = 60;//1小时=60分钟；
const int Day_to_hour = 24;//1天=24小时；

long long whole_seconds;

cout << "Enter the number of seconds: ";
cin >> whole_seconds;
int days = whole_seconds / (Minute_to_second*Hour_to_minute*Day_to_hour);
int hours = (whole_seconds % (Minute_to_second*Hour_to_minute*Day_to_hour)) / (Minute_to_second*Hour_to_minute);
int minutes = ((whole_seconds % (Minute_to_second*Hour_to_minute*Day_to_hour)) % (Minute_to_second*Hour_to_minute))/(Hour_to_minute);
int seconds = ((whole_seconds % (Minute_to_second*Hour_to_minute*Day_to_hour)) % (Minute_to_second*Hour_to_minute)) % (Hour_to_minute);
cout << whole_seconds << " seconds = " << days << " days, " << hours << " hours, " << minutes << " minutes, " << seconds << " seconds\n";

return 0;

}