Analyse et algorithme

program ala;
uses wincrt;
var ch1,ch2,ch3,ch4:string;
begin
writeln ('donner le nom et la moiyenne de 1');
readln (ch1);
writeln ('donner 2');
readln (ch2);
writeln ('donner 3');
readln (ch3);
delete (ch1,1,6);
delete (ch2,1,6);
delete (ch3,1,6);
ch4:= concat(ch1,' ',ch2,' ',ch3);
writeln (ch4)
end.
j'ai fais le programme mais je suis nul on analyse et algorithme, votre aide svp