C :

#include<stdio.h>

int pre[100];
int path1[100],path2[100];

int main(){
	int x,y,i,j,k;
	scanf("%d %d",&x,&y);
	int a,b;
	while(scanf("%d %d",&a,&b)==2){
		pre[a]=b;
	}
	i=j=0;
	path1[i]=x;
	path2[j]=y;
	while(pre[x]!=0){
		i++;
		path1[i]=pre[x];
		x=pre[x];
	}
	while(pre[y]!=0){
		j++;
		path2[j]=pre[y];
		y=pre[y];
	}
	while(path1[i]==path2[j]){
		i--;
		j--;
	}
	for(k=0;k<=i+1;k++){
		printf("%d ",path1[k]);
	}
	for(k=j;k>=0;k--){
		printf("%d ",path2[k]);
	}
} 

C++ :

#include<cstdio>
#include<stack>
using namespace std;
const int N=100;
int x,y;
int f[N];
bool g[N];
stack<int>s;
int main()
{
	int a,b;
	scanf("%d%d",&x,&y);
	for(int i=1;i<N;i++)
		f[i]=i;
	while(scanf("%d%d",&a,&b)!=EOF&&a)
		f[a]=b;
	if(x==y)
		printf("%d",x);
	else
	{
		a=x,b=y;
		g[x]=true;
		while(x!=f[x])
			x=f[x],g[x]=true;
		while(g[y]!=true)
			y=f[y],s.push(y);
		g[y]=false;
		while(g[a]==true)
			printf("%d ",a),a=f[a];
		while(!s.empty())
			printf("%d ",s.top()),s.pop();
		printf("%d",b);
	}
	return 0;
}

Pascal :

program qi26885;
var
 x,y,m,n,root:longint;
 father,a:array[1..100]of longint;
procedure du;
begin
 readln(x,y);
 while not eof do
  begin
   readln(m,n);
   father[m]:=n;
  end;
end;
procedure find;
var
 i,j:longint;
begin
 i:=x;
 while i<>0 do
  begin
   a[i]:=1;
   i:=father[i]
  end;
 j:=y;
 while a[j]<>1 do j:=father[j];
 root:=j;
end;
procedure finda(i:longint);
begin
 if i<>root then
  begin
   write(i,' ');
   finda(father[i]);
  end;
end;
procedure findb(i:longint);
begin
 if i<>root then
  begin
   findb(father[i]);
   if i<>y then write(i,' ') else writeln(i);
  end;
end;
begin
 du; find;
 finda(x);
 write(root,' ');
 findb(y);
end.