procedure TRIDAG(A, B, C, R:array of real;var U:array of real; N:integer);
var
    GAM:array[0..100] of real;
    J:integer;  BET:real;
begin
    If B[1] = 0 Then Exit;
    BET:=B[1];
    U[1]:=R[1] / BET;
    For J:=2 To N do
    begin
        GAM[J]:=C[J - 1] / BET;
        BET:=B[J] - A[J] * GAM[J];
        If BET = 0 Then Exit;
        U[J]:=(R[J] - A[J] * U[J - 1]) / BET;
    end;
    For J:=N - 1 DownTo 1 do
        U[J]:=U[J] - GAM[J + 1] * U[J + 1];
end;