package main

import (
	"fmt"
)

func main() {
	var s1, s2 string
	fmt.Scan(&s1, &s2)
	var hs, ms, ht, mt int
	fmt.Sscanf(s1, "%d:%d", &hs, &ms)
	fmt.Sscanf(s2, "%d:%d", &ht, &mt)

	tp := (hs*60 + ms - (ht*60 + mt) + 1440) % 1440
	fmt.Printf("%02d:%02d\n", tp/60, tp%60)
}