f1(Foo(1)) == true
f1(Foo(1, 2)) == false
f1(Foo(1, 2, 3)) == false

f2(Foo(1)) == false
f2(Foo(1, 2)) == true
f2(Foo(1, 2, 3)) == false

f3(Foo(1)) == false
f3(Foo(1, 2)) == false
f3(Foo(1, 2, 3)) == true

f1seq(Foo(1)) == true
f1seq(Foo(1, 2)) == true
f1seq(Foo(1, 2, 3)) == true

f2seq(Foo(1)) == false
f2seq(Foo(1, 2)) == true
f2seq(Foo(1, 2, 3)) == true

f3seq(Foo(1)) == false
f3seq(Foo(1, 2)) == false
f3seq(Foo(1, 2, 3)) == true