#include<bits/stdc++.h>
using namespace std;
int time_seconds,time_minutes,time_hours,pass_seconds,pass_minutes;
int main()
{
    cin>>time_seconds;
    time_minutes=time_seconds/60;
    time_hours=time_minutes/60;
    pass_seconds=time_seconds%60;
    pass_minutes=time_minutes%60;
	if(time_seconds<60&&time_seconds>=10)
	cout<<"00:00:"<<pass_seconds<<endl;
	else if(time_seconds<10)
	cout<<"00:00:0"<<time_seconds<<endl;
	else if(time_minutes<60&&pass_minutes>=10&&pass_seconds>=10)
	cout<<"00:"<<pass_minutes<<":"<<pass_seconds<<endl;
	else if(time_minutes<60&&pass_minutes<10&&pass_seconds<10)
	cout<<"00:0"<<pass_minutes<<":0"<<pass_seconds<<endl;
	else if(time_minutes<60&&pass_minutes<10&&pass_seconds>=10)
	cout<<"00:0"<<pass_minutes<<":"<<pass_seconds<<endl;
	else if(time_minutes<60&&pass_minutes>=10&&pass_seconds<10)
	cout<<"00:"<<pass_minutes<<":0"<<pass_seconds<<endl;
	else if(time_hours>=10&&pass_minutes>=10&&pass_seconds>=10)
	cout<<time_hours<<":"<<pass_minutes<<":"<<pass_seconds<<endl;
	else if(time_hours<10&&pass_minutes>=10&&pass_seconds>=10)
	cout<<"0"<<time_hours<<":"<<pass_minutes<<":"<<pass_seconds<<endl;
	else if(time_hours<10&&pass_minutes<10&&pass_seconds>=10)
	cout<<"0"<<time_hours<<":0"<<pass_minutes<<":"<<pass_seconds<<endl;
	else if(time_hours>=10&&pass_minutes<10&&pass_seconds<10)
	cout<<time_hours<<":0"<<pass_minutes<<":0"<<pass_seconds<<endl;
	else if(time_hours<10&&pass_minutes<10&&pass_seconds<10)
	cout<<"0"<<time_hours<<":0"<<pass_minutes<<":0"<<pass_seconds<<endl;
	else if(time_hours>=10&&pass_minutes<10&&pass_seconds>=10)
	cout<<time_hours<<":0"<<pass_minutes<<":"<<pass_seconds<<endl;
	else if(time_hours>=10&&pass_minutes>=10&&pass_seconds<10)
	cout<<time_hours<<":"<<pass_minutes<<":0"<<pass_seconds<<endl;
}

有没有更好的方法啊，这样打好累……