#include <iostream>

using namespace std;

int main()
{
    unsigned int a;
    cin>>a;
    if ((a>=1) and (a<=4)) cout<<"few";
    if ((a>=5) and (a<=9)) cout<<"several";
    if ((a>=10) and (a<=19)) cout<<"pack";
    if ((a>=20) and (a<=49)) cout<<"lots";
    if ((a>=50) and (a<=99)) cout<<"horde";
    if ((a>=100) and (a<=249)) cout<<"throng";
    if ((a>=250) and (a<=499)) cout<<"zwarm";
    if ((a>=500) and (a<=999)) cout<<"zounds";
    if ((a>=1000) and (a<=2000)) cout<<"legion";
     return 0;
}

Why??

"swarm", not "zwarm" :D

What for people have invented case??? I don't know)