{$N+}Program M;

CONST
     n=20;
     bodu=100;
TYPE
    vektor=array[1..n] of real;

VAR
   i,j:integer;
   xn,yn,An,Bn,Cn,Dn,krok:real;
   a,b,c,x,y,y2,rho,mu,f:vektor;
   filein,fileout:text;
BEGIN

ASSIGN(filein,'vst.dat');
ASSIGN(fileout,'vystup.dat');
RESET(filein);
REWRITE(fileout);

FOR i:=1 TO n DO
BEGIN
    	READ(filein,x[i]);
	READ(filein,y[i]);
	rho[i]:=0;
	mu[i]:=0;
	y2[i]:=0;
END;

FOR i:=2 TO n-1 DO
BEGIN
	c[i]:=(x[i]-x[i-1])/6;
        a[i]:=(x[i+1]-x[i-1])/3;
	b[i]:=(x[i+1]-x[i])/6;
	f[i]:=(y[i+1]-y[i])/(x[i+1]-x[i])-(y[i]-y[i-1])/(x[i]-x[i-1]);
END;

FOR i:=2 TO n-1 DO
BEGIN
    mu[i+1]:=-b[i]/(c[i]*mu[i]+a[i]);
    rho[i+1]:=(f[i]-c[i]*rho[i])/(c[i]*mu[i]+a[i]);
END;

FOR i:=n-1 DOWNTO 2 DO y2[i]:=mu[i+1]*y2[i+1]+rho[i+1];

{FOR i:=1 TO n DO WRITELN(y2[i]:7:3);}

krok:=(x[n]-x[1])/(bodu-1);
xn:=x[1];

FOR i:=1 TO bodu DO BEGIN
	j:=1;
	WHILE (x[j]<=xn) DO BEGIN
	   IF (j=n) THEN BREAK;
	   j:=j+1;
	END;
        j:=j-1;
	An:=(x[j+1]-xn)/(x[j+1]-x[j]);
	Bn:=1-An;
	Cn:=An*(An*An-1)*(x[j+1]-x[j])*(x[j+1]-x[j])/6;
	Dn:=An*(An*An-1)*(x[j+1]-x[j])*(x[j+1]-x[j])/6;
	yn:=An*y[j]+Bn*y[j+1]+Cn*y2[j]+Dn*y2[j+1];
	WRITELN(fileout,xn:5:3,' ',yn:5:3);
	xn:=xn+krok;
END;

CLOSE(filein);
CLOSE(fileout);

WRITELN('Hotovo');
READLN;

END.