C :

#include<stdio.h>
int main( int argc, char **argv )
{
	int n, m;
	while( scanf( "%d%d", &n, &m ) != EOF )
	{
		int i;
		for( i = n; i < m; i++ )
			printf( "%d ", i );
		for( i = m; i >= n; i-- )
			printf( "%d ", i );
	}
	return 0;

}

C++ :

//输出合唱队形.cpp
#include<iostream>
using  namespace  std;
int  main()
{
    int  n,m;
    cin>>n>>m;
    for(int i=n;i<=m;i++){cout<<i<<" ";}
    for(int i=m-1;i>=n;i--){cout<<i<<" ";}
    return 0;
}