帮我看看这题怎么写吧

#include <iostream>
using namespace std;
int main()
{
    int h1,m1,s1,h2,s2,m2,a,b,c;
    scanf("%d:%d:%d",&h2,&m2,&s2);   
    scanf("%d:%d:%d",&h1,&m1,&s1);
    a=h2-h1;
    b=m2-m1;
    c=s2-s1;
    if(c<0)
    {
        c+=60;
        b--;
    }
    if(b<0)
    {
        b+=60;
        a--;
    }
    cout<<a*3600+b*60+c<<endl;
    return 0;
}