题解

#include<iostream>
using namespace std;
int main(){
    int t;
    cin>>t;
    if(t/3600<10){
        cout<<"0";
    }
    cout<<t/3600<<":";
    if(t%3600/60<10){
        cout<<"0";
    }
    cout<<t%3600/60<<":";
    if(t%3600%60<10){
        cout<<"0";
    }
    cout<<t%3600%60;
}