请问编译时为什么不能通过，程序目的是每个字母变为后四位的字母如a变为e

#include<iostream>
using namespace std;
class M
{public:M(char t1,char t2,char t3,char t4,char t5)
{
c1=t1;
c2=t2,c3=t3,c4=t4,c5=t5;
}

void change()
{
    c1+=4;
    c2+=4;
    c3+=4;
    c4+=4;
    c5+=4;
    cout<<c1<<c2<<c3<<c4<<c5;
}
private:
    char c1;
    char c2;
    char c3,c4,c5;

};
int mian()
{
    M c('C','l','m','r','e');
    c.change();
    return 0;
}