import std.stdio;
import std.datetime;
import std.conv;

void main()
{
	auto s = TimeOfDay.fromISOExtString(readln[0 .. $-1] ~ ":00");
	auto t = readln;
	auto d = dur!"hours"((t[0..2]).to!long)
		   + dur!"minutes"(t[3..5].to!long);
	writeln((s - d).toISOExtString[0..5]);
}