C :

#include "stdio.h"
int n,l,m;
int a[32];
int C(int n,int a)
{
	int i,j;
	long long s;
	if(a<n-a)
		a=n-a;
	s=1,j=2;
	for(i=a+1;i<=n;i++)
	{
		s*=i;
		while(j<=n-a&&s%j==0)
		{
			s/=j;
			j++;
		}
	}
	return s;
}
int F(int d)
{
	int i,s;
	s=0;
	for(i=0;i<=l&&i<d;i++)
		s+=C(d-1,i);

	return s;
}
void print()
{
	int i;
	for(i=n-1;i>=0;i--)
		printf("%d",a[i]);
	printf("\n");
}
int main()
{
	int i,t;
	scanf("%d%d%d",&n,&l,&m);
	for(i=n;i>=1;i--)
	{
		if(m==1||m==2)
		{
			a[0]=m-1;
			break;
		}
		t=F(i);
		if(t<m)
		{
			a[i-1]=1;
			l--;
			m-=t;
		}
	}
	print();
	return 0;
}

C++ :

#include<cstdio>
using namespace std;
int f(int aa,int bb)
{
	int ll=1;
	while(bb)
	{
		if(bb&1)
		ll=ll*aa;
		aa=aa*aa;
		bb>>=1;
	}
	return ll;
}
int main()
{
	int N,L,i,j,k,ss;
	scanf("%d %d %d",&N,&L,&i);
	ss=f(2,L+1)-1;
	if(i<=ss)
	{
		int q=i-1,c[35]={0},qq=N;
		while(q)
		{
			c[qq-1]=q%2;
			q/=2;
			qq--;
		}
		for(k=0;k<N;k++)
		printf("%d",c[k]);
		return 0;
	}
	for(j=ss+1;;j++)
	{
		
		int t=j,a[35]={0},h=N,count=0;
		while(t)
		{
			a[h-1]=t%2;
			t/=2;
			h--;
		}
		for(k=0;k<N;k++)
		{
			if(a[k]==1)
			count++;
		}
		if(count>L)
		continue;
		else 
		{
			ss++;
			if(ss==i)
			{
				for(k=0;k<N;k++)
				printf("%d",a[k]);
				return 0;
			}
		}
	}
}

Pascal :

program kimbits;
var pos:array[0..35] of longint;
    f:array[0..35,0..35] of longint;
    i,j,l,n,k:longint;
function min(a,b:longint):longint;
begin
 if a<b then exit(a)
  else exit(b);
end;

procedure comeout(a,b,c:longint);
var tip:longint;
begin
 if a=0 then exit;
 tip:=f[a-1,b];
 if tip<c then
  begin
   write('1');
   comeout(a-1,b-1,c-tip);
  end
 else
  begin
   write('0');
   comeout(a-1,b,c);
  end;
end;

begin
readln(n,l,i);
for k:=0 to n do
 f[k,0]:=1;
for k:=0 to l do
 f[0,k]:=1;
for k:=1 to n do
 for j:=1 to l do
  f[k,j]:=f[k-1,j]+f[k-1,j-1];
comeout(n,l,i);
end.