rsa算法，输入密文后解出明文和之前输入的明文不一样，

问题相关代码，请勿粘贴截图

#include<windows.h>
#include<iostream>
#include<math.h>
#include<stdio.h>
using namespace std;
typedef int Elemtype;
Elemtype p, q, e;
Elemtype fn;
Elemtype m, c;
int flag = 0;
typedef void(*Msghandler)(void);
struct MsgMap
{
    char ch;
    Msghandler handler;
};
 
/*公钥*/
struct PU
{
    Elemtype e;
    Elemtype n;
} pu;
 
/*私钥*/
struct PR
{
    Elemtype d;
    Elemtype n;
} pr;
 
/*判定一个数是否为素数*/
bool test_prime(Elemtype m)
{
    if (m <= 1)
    {
        return false;
    }
    else if (m == 2)
    {
        return true;
    }
    else
    {
        for (int i = 2; i <= sqrt(m); i++)
        {
            if ((m % i) == 0)
            {
                return false;
                break;
            }
        }
        return true;
    }
}
 
/*将十进制数据转化为二进制数组*/
void switch_to_bit(Elemtype b, Elemtype bin[32])
{
    int n = 0;
    while (b > 0)
    {
        bin[n] = b % 2;
        n++;
        b /= 2;
    }
}
 
/*初始化主界面*/
void Init(){
cout<<"******************************************"<<endl;
cout<<"***     Welcome to use RSA encoder     ***"<<endl;
cout<<"***            1.setkey                ***"<<endl;
cout<<"***            2.加密                  ***"<<endl;
cout<<"***            3.解密                  ***"<<endl;
cout<<"***            4.退出                  ***"<<endl;
cout<<"******************************************"<<endl;
cout<<"press a key:"<<endl;
}
 
/*将两个数排序，大的在前面*/
void order(Elemtype &in1, Elemtype &in2)
{
    Elemtype a = (in1 > in2 ? in1 : in2);
    Elemtype b = (in1 < in2 ? in1 : in2);
    in1 = a;
    in2 = b;
}
 
/*求最大公约数*/
Elemtype gcd(Elemtype a, Elemtype b)
{
    order(a, b);
    int r;
    if (b == 0)
    {
        return a;
    }
    else
    {
        while (true)
        {
            r = a % b;
            a = b;
            b = r;
            if (b == 0)
            {
                return a;
                break;
            }
        }
    }
}
 
/*用扩展的欧几里得算法求乘法逆元*/
Elemtype extend_euclid(Elemtype m, Elemtype bin)
{
    order(m, bin);
    Elemtype a[3], b[3], t[3];
    a[0] = 1, a[1] = 0, a[2] = m;
    b[0] = 0, b[1] = 1, b[2] = bin;
    if (b[2] == 0)
    {
        return a[2] = gcd(m, bin);
    }
    if (b[2] == 1)
    {
        return b[2] = gcd(m, bin);
    }
    while (true)
    {
        if (b[2] == 1)
        {
            return b[1];
            break;
        }
        int q = a[2] / b[2];
        for (int i = 0; i < 3; i++)
        {
            t[i] = a[i] - q * b[i];
            a[i] = b[i];
            b[i] = t[i];
        }
    }
}
 
/*快速模幂算法*/
Elemtype modular_multiplication(Elemtype a, Elemtype b, Elemtype n)
{
    Elemtype f = 1;
    Elemtype bin[32];
    switch_to_bit(b, bin);
    for (int i = 32; i >= 0; i--)
    {
        f = (f * f) % n;
        if (bin[i] == 1)
        {
            f = (f * a) % n;
        }
    }
    return f;
}
 
/*产生密钥*/
void produce_key()
{
    cout << "输入素数 p 和 q:";
    cin >> p >> q;
    while (!(test_prime(p) && test_prime(q)))
    {
        cout << "输入错误，请重新输入!" << endl;
        cout << "输入素数 p 和 q:";
        cin >> p >> q;
    };
    pr.n = p * q;
    pu.n = p * q;
    fn = (p - 1) * (q - 1);
    cout << "fn为：" << fn << endl;
    cout << "输入随机数e:";
    cin >> e;
    while ((gcd(fn, e) != 1))
    {
        cout << "e输入错误，请重新输入!" << endl;
        cout << "输入随机数e:";
        cin >> e;
    }
    pr.d = (extend_euclid(fn, e) + fn) % fn;
    pu.e = e;
    flag = 1;
    cout << "公钥(e,n）:" << pu.e << "," << pu.n << endl;
    cout << "私钥d:" << pr.d << endl;
    cout << "请输入下一步操作序号:" << endl;
}
 
/*加密*/
void encrypt()
{
    if (flag == 0)
    {
        cout << "setkey first:" << endl;
        produce_key();
    }
    cout << "输入明文 m:";
    cin >> m;
    c = modular_multiplication(m, pu.e, pu.n);
    cout << "密文c 为:" << c << endl;
    cout << "请输入下一步操作序号:" << endl;
}
/*解密*/
void decrypt()
{
    if (flag == 0)
    {
        cout << "setkey first:" << endl;
        produce_key();
    }
    cout << "输入密文 c:";
    cin >> c;
    m = modular_multiplication(c, pr.d, pr.n);
    cout << "明文m 为:" << m << endl;
    cout << "请输入下一步操作序号:" << endl;
}
/*消息映射*/
MsgMap Messagemap[] =
{
    { '1', produce_key },
    { '3', decrypt },
    { '2', encrypt },
    { '4', NULL }
};
 
/*主函数，提供循环*/
int main()
{
    Init();
    char d;
    while ((d = getchar()) != '4')
    {
        int i = 0;
        while (Messagemap[i].ch)
        {
            if (Messagemap[i].ch == d)
            {
                Messagemap[i].handler();
                break;
            }
            i++;
        }
    }
   
   
  
}

运行结果及报错内容

我想要达到的结果

使输出明文和输入的明文一致