帮我看下，无法输出？？？

#include<iostream>
using namespace std;
class stud{
public:
    void setinformation(long x,char y);
    void showinformation();
private:
    long studnum;
    char studsex;
};
void stud::setinformation(long x,char y){
    studnum=x;
    studsex=y;
}
void stud::showinformation (){
    if(studnum=='g')
       cout<<"mike is a girl and her studnum is:"<<studnum<<endl;
    if(studnum=='b')
        cout<<"mike is a boy and his studnum is:"<<studnum<<endl;
}
int main(){
    stud mike;
    long num;
    char sex;
    cout<<"input num:"<<endl;
    cin>>num;
    cout<<"input sex:"<<endl;
    cin>>sex;
    mike.setinformation(num,sex);
    mike.showinformation();
    return 0;
}