RSA Algorithm

#include<bits/stdc++.h>
using namespace std;

int expmod(int x, int y, int n)
{
    int r=1;
    while(y>0)
    {
        if((int)(y%2)==1)
            r=(r*x)%n;
        x=(x*x)%n;
        y=y/2;
    }
    return(r);
}

int main(){
    int p,q;
    char msg[100];
    cout << "Enter 2 prime numbers\n";
    cin >> p >> q;
    int n = p*q, z = (p-1)*(q-1);
    cout << "Choose any prime number e lower than " << z << endl;
    int e;
    cin >> e;
    int d = 1;
    while((e*d)%z!=1){
        d++;
    }
    printf("\n public key (%d,%d)",e,n);
    printf("\n private key (%d,%d)",d,n);
    printf("\nEnter Message\n");
    cin >> msg;
    cout << "\nplaintext \n";

    int plain[100],cipher[100],plain2[100];
    for(int i=0; i<strlen(msg); i++){
        plain[i]=msg[i];
        printf("%d\t%c\n",plain[i],plain[i]);
    }

    cout << "\nCiphertext after Encryption\n";
    for(int i=0; i<strlen(msg); i++){
        cipher[i]=expmod(plain[i],e,n);
        printf("%d\t%c\n",cipher[i],cipher[i]);
    }
    cout << "\nplaintext after Decryption\n";
    for(int i=0; i<strlen(msg); i++){
        plain2[i]=expmod(cipher[i],d,n);
        printf("%d\t%c\n",plain2[i],plain2[i]);
    }
}

/*
OUTPUT

Enter 2 prime numbers
17 23
Choose any prime number e lower than 352
3

 public key (3,391)
 private key (235,391)
Enter Message
LOVE

plaintext
76  L
79  O
86  V
69  E

Ciphertext after Encryption
274 
379 {
290 "
69  E

plaintext after Decryption
76  L
79  O
86  V
69  E


*/