Procedure ELMHES(var A:matrx2; N:integer);
var
    M,J,I:integer;  X,Y:real;
begin
    If N > 2 Then
    begin
        For M:=2 To N - 1 do
        begin
            X:=0 ;
            I:=M;
            For J:=M To N do
            begin
                If Abs(A[J, M - 1]) > Abs(X) Then
                begin
                    X:=A[J, M - 1];
                    I:=J;
                end;
            end; 
            If I <> M Then
            begin
                For J:=M - 1 To N do
                begin
                    Y:=A[I, J];
                    A[I, J]:=A[M, J];
                    A[M, J]:=Y;
                end;
                For J:=1 To N do
                begin
                    Y:=A[J, I];
                    A[J, I]:=A[J, M];
                    A[J, M]:=Y;
                end; 
            end;
            If X <> 0  Then
            begin
                For I:=M + 1 To N do
                begin
                    Y:=A[I, M - 1];
                    If Y <> 0  Then 
                    begin
                        Y:=Y / X;
                        A[I, M - 1]:=Y;
                        For J:=M To N do
                            A[I, J]:=A[I, J] - Y * A[M, J];
                        For J:=1 To N do
                            A[J, M]:=A[J, M] + Y * A[J, I];
                    end;
                end; 
            end;
        end; 
    end;
end;