Câu 1:
uses crt;
var n,t:longint;
begin
clrscr;
repeat
readln(n);
until n<500;
n:=2*n+1;
t:=((n+1)*(((n-1) div 2) + 1)) div 2;
writeln(t);
readln;
end.
Câu 2:
var f1,f2:text;
s:string;
begin
assign(f1,'xau.inp');reset(f1);
assign(f2,'xau.out');rewrite(f2);
readln(f1,s);
while s[1] = ' ' do delete(s,1,1);
while s[length(s)] = ' ' do delete(s,length(s),1);
writeln(f2,s);
close(f1);close(f2);
readln;
end.
Câu 3:
uses crt;
var i,n,t,dem:word;
a:array[1..1000] of longint;
begin
t:=0;dem:=0;
repeat
readln(n);
until (0<n) and (n<1000);
for i:=1 to n do
begin
readln(a[i]);
if a[i] > 0 then
begin
t:=t+a[i];
inc(dem);
end;
end;
writeln(t/dem:0:3);
readln;
end.
