Обратная матрица

program inverse;
var
    a: array[1..10, 1..20] of double;
    n, i, j, k: Integer;
    t: double;
begin
    Write('Size of matrix =');
    ReadLn(n);
    for i := 1 to n do
        for j := 1 to n do begin
            Write('a[',i,',',j,']=');
            ReadLn(a[i,j])
        end;
    for i := 1 to n do begin
        for j := 1 to n do a[i,n+j] := 0.0;
        a[i,n+i] := 1.0;
    end;
    for i := 1 to n do begin
        t := abs(a[i,i]);
        k := i;
        for j := i+1 to n do
            if abs(a[j,i]) > t then begin
                t := abs(a[j,i]);
                k := j;
            end;
        for j := 1 to 2*n do begin
            t := a[i,j];
            a[i,j] := a[k,j];
            a[k,j] := t;
        end;
        t := 1.0/a[i,i];
        for j := 1 to 2*n do a[i,j] := a[i,j]*t;
        for j := i+1 to n do begin
            t := a[j,i];
            for k := 1 to 2*n do
                a[j,k] := a[j,k]-a[i,k]*t;
        end
    end;
    for i := n downto 2 do begin
        for j := i-1 downto 1 do begin
            t := a[j,i];
            for k := i to 2*n do
                a[j,k] := a[j,k]-a[i,k]*t;
        end;
    end;
    for i := 1 to n do begin
        for j := 1 to n do
            Write(a[i,n+j]:8:3, ' ');
        WriteLn;
    end;
end.