Составить таблицу истинности для формул: а) (а<->в) ∆ (-, в -> с)б) (а ∆ в v c -> (-, a <-> c)в) (A v B) ∆ ( -, A v C ) -> (B <-> C)

1.
uses crt;
var n:string;
begin
read(n); 
writeln(strtoint(n[1])*strtoint(n[2])*strtoint(n[3]));
end.
2.
uses crt;
var n,i:integer;
res:double;
begin
read(n);
for i:=1 to n do
res:=res+cos(1/i);
writeln(res:5:3);
end.
3.
uses crt;
var n,i:integer;
mult:real;
a:array[1..100] of real;
begin
mult:=1;
writeln('Input N and elements of array.');
read(n);
for i:=1 to n do
begin
read(a[i]);
if i mod 2=0 then 
mult:=mult*a[i];
end; 
writeln(mult);
end.
4.
uses crt;
var n,i,sum:integer;
a:array[1..100] of integer;
begin
writeln('Input N and elements of array.');
read(n);
for i:=1 to n do
read(a[i]);
i:=1;
while (a[i]<>0) and (i<=n) do
begin
if a[i] mod 2=0 then
sum:=sum+a[i];
i:=i+1;
end;
writeln(sum);
end.