Codechef magic trick problem coded in C!

    #include<stdio.h>
    #include<string.h>
    typedef unsigned long long int ll;
    ll a[1000000];
    char s[1000000];
    ll mul(ll a1,ll b1,ll c1)
    {
    ll pro=0;
    b1=b1%c1;
    while(a1)
    {
    if(a1&1)
    {
    pro=pro+=b1;
    if(pro>c1) pro=pro-c1;
    }
    a1>>=1;
    b1<<=1;
    if(b1>c1)
    b1=b1-c1;
    }
    return pro;

    }

    #define getcx getchar_unlocked
    inline void fscan(ll *a )
    {
    ll n=0; int ch = getcx(); int sign = 1;
    while(ch < '0' || ch > '9')
    {
    if(ch == '-') sign=-1; ch = getcx();
    }
    while(ch >= '0' && ch <= '9')
    {
    n = (n << 3) + (n << 1) + ch - '0', ch = getcx();
    }
    *a = n * sign;
    }

    int main()
    {
    ll i,j,k,l,m,n,t,x,y,z,temp1,temp2;
    fscan(&t);

    while(t--)
    {
    fscan(&n);
    for(i=0;i<n;i++)
    fscan(&a[i]);
    fscan(&x);
    fscan(&y);
    fscan(&z);
    scanf("%s",s);



    l=strlen(s);
    ll end=n-1,count=n,min=0,max=n-1,revcount=0;
    i=0;
    for(count=0;count<n;count++)
    {

    if(s[count]=='A')
    {
    for(j=min;j<=max;j++)
    {
    a[j]=(a[j]+x)%z;
    }
    printf("%lld ",a[i]);
    if(((revcount&1))==1) i--;
    else i++;
    }

    else if(s[count]=='M')
    {
    for(j=min;j<=max;j++)
    {
    a[j]=mul(a[j],y,z);
    }
    printf("%lld ",a[i]);
    if(((revcount&1))==1) i--;
    else i++;

    }
    else
    {
    printf("%lld ",a[end]%z);
    if(end>=i)
    temp1=end-1;
    else
    temp1=end+1;

    temp2=temp1;
    temp1=i;
    i=temp2;
    end=temp1;
    revcount++;
    if(end>i)
    {
    min=i;max=end;
    }
    else
    {
    min=end;max=i;
    }
    }

    }

    printf("\n");
    }
    return 0;
    }