program z_4; uses crt; var x,x1,x2,x3,s,n,i:integer; begin clrscr; writeln ('vvedite n'); readln (n); s:=0; for i:=1 to n-1 do begin write ('->'); readln (x,x1,x2,x3); x1:=x2; x2:=x3; x3:=x; s:=x1+x2+x3; if ((x3>0)and(s=x3)) then writeln ('pervy poloshitelniy element naiden=',x3); readln (x3); end; readln; readln; end.