coding_decoding

#include <stdio.h>
#include <stdlib.h>

int main()
{
    char para[2000000];
    printf("Enter a string-");
    scanf("%[^\n]",&para);  //scanning the whole string, including the white spaces
    printf("%s\n",para);

int before,after;
char alphabet[]={'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
char number[]={'0','1','2','3','4','5','6','7','8','9'};
for(int i=0;i<2000000;i++)
{
    for(int j=0;j<26;j++)
    {
        before=j+13;
        after=j-13;
        if(para[i]==alphabet[j])
        {
            if(j<13)
                para[i]=alphabet[before];

            else
                para[i]=alphabet[after];
                break;
        }
    }
    for(int j=0;j<10;j++)
    {
        before=j+5;
        after=j-5;
        if(para[i]==number[j])
        {
            if(j<5)
                para[i]=number[before];
            else
                para[i]=number[after];
                break;
        }
    }
}printf("%s",para);
return 0;
}