в си++ ошибка switch quantity not an integer что не так?

#include <iostream.h>
#include <math.h>

int main()
{float k, a, b, q;
cout << ("\nVvelbnt nomer mesyaca");
cout << ("\n1=yanvar");
cout << ("\n2=aevral");
cout << ("\n3=mart");
cout << ("\n4=aprel");
cout << ("\n5=may");
cout << ("\n6=iun");
cout << ("\n7=iul");
cout << ("\n8=avgust");
cout << ("\n9=sentaybr");
cout << ("\n10=oktaybr");
cout << ("\n11=noyabr");
cout << ("\n12=dekabr\n");
cin >> a;
if((a==0)|(a>12))
{cout << ("Neverniy mesayc\n");
cin >> q;
abort();}
cout << ("\nVvedite k");
cin >> k;
b=a+k;
while(b>12)
{b=b-12;}
switch (a){
case 1: cout << ("\nYanvar"); break;
case 2: cout << ("\nFevral"); break;
case 3: cout << ("\nMart"); break;
case 4: cout << ("\nAprel"); break;
case 5: cout << ("\nMay"); break;
case 6: cout << ("\nIun"); break;
case 7: cout << ("\nIul"); break;
case 8: cout << ("\nAvgust"); break;
case 9: cout << ("\nSentaybr"); break;
case 10: cout << ("\nOktaybr"); break;
case 11: cout << ("\nNoyabr"); break;
case 12: cout << ("\nDekabr\n"); break;}
cin >> q;
}