let m, n be Nat; :: thesis: ( not m * n = 122 or ( m = 1 & n = 122 ) or ( m = 2 & n = 61 ) or ( m = 61 & n = 2 ) or ( m = 122 & n = 1 ) )
assume A1: m * n = 122 ; :: thesis: ( ( m = 1 & n = 122 ) or ( m = 2 & n = 61 ) or ( m = 61 & n = 2 ) or ( m = 122 & n = 1 ) )
m divides m * n ;
then ( m = 1 or m = 2 or m = 61 or m = 122 ) by A1, Th19;
hence ( ( m = 1 & n = 122 ) or ( m = 2 & n = 61 ) or ( m = 61 & n = 2 ) or ( m = 122 & n = 1 ) ) by A1; :: thesis: verum