For...to...do:
uses crt;
var i,n:longint; s:real;
begin
clrscr;
write('Nhap N: ');readln(n);
s:=0;
for i:=1 to n do s:=s+1/(i*i);
writeln('s=',s:0:2);
readln;
end.
While...do:
uses crt;
var i,n:longint; s:real;
begin
clrscr;
write('Nhap N: ');readln(n);
s:=0;
i:=0;
while (i<n) do begin inc(i); s:=s+1/(i*i); end;
writeln('s=',s:0:2);
readln;
end.