【问题】求高手指点

#include "stdafx.h"
#include <windows.h>
#include <iostream>
using namespace std; int _tmain(int argc, _TCHAR* argv[])
{
int iNum1,iNum2,iNum3;
char cNum4;
cin>>iNum1,cNum4,iNum2;
switch (cNum4)
{
case '+':
iNum3=iNum1+iNum2;
cout<<"iNum3";
break;
}
system ("pause");
return 0;
}
调试的时候出现
Run-Time Check Failure #3 - The variable 'cNum4' is being used without being initialized.