Name reduction Query( May Challenge)

I submitted this code and got WA. Could someone please tell me why I am getting WA despite it working perfectly in my computer.

Link to the problem:

Name reduction

Here is my code:

//name red 2
#include<iostream>
#include<cstring>
#include<cmath>
#define l 42000
using namespace std;

int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {


    char a[l],b[l],c[l],alpha[27]={0};
    scanf("%s",a);
    scanf("%s",b);

    for(int j=0;j<strlen(a);j++)
    {
        // a[j]=tolower(a[j]);
        alpha[a[j]-'0'-97]++;
    }
      for(int k=0;k<strlen(b);k++)
    {
        //b[k]=tolower(b[k]);
        alpha[b[k]-'0'-97]++;
    }

    int flag=0;
    int n;
    scanf("%d",&n);
    while(n--)
    {
        scanf("%s",c);
       // cin.ignore();

        for(int i=0;i<strlen(c);i++)
        {
            alpha[c[i]-'0'-97]--;
            if((alpha[c[i]-'0'-97])<0)
            {
                flag=1;
                break;
            }
        }


    }
     if(flag==0)
        printf("YES\n");
        else
        printf("NO\n");


    }

}

The logic I am using is: I have created an array of size 26 corresponding to all the alphabets in English language. For each letter in parent, the count is incremented. Letter 'a' is array[0] and 'z' is array[25]. Then from each of the children I decrement the alphabets. As soon as a negative number appears in the array, NO is ouput, otherwise I output YES. Could someone please clarify why this code was leading to WA.