uses crt;
var
kx1,kx2,ky1,ky2:real;
function c(x1,y1,x2,y2:real):real;
begin
c:=sqrt(((x2-x1)*(x2-x1))+((y2-y1)*(y2-y1)));
end;
begin
clrscr;
writeln('vvedite koordinati 1 vershini');
readln(kx1,ky1);
writeln('vvedite koordinati sosedney vershini');
readln(kx2,ky2);
writeln('P=',4*c(kx1,ky1,kx2,ky2):4:1);
readln;
end.