Assignment_P_GCD_FACT

#include<stdio.h>
#include<math.h>
#define ll  long long int

ll fact(ll n)
{
    ll i,s=1;
    for(i=2; i<=n; i++)
        s*=i;
    return s;
}
ll prime(ll n)
{
    ll i,j;
    if(n==1)
        return 0;
    else if(n%2==0 && n!=2)
        return 0;
    else
    {
        for(i=3; i*i<=n; i+=2)
        {
            if(n%i==0 && n!=i)
                return 0;
        }
    }
    return 1;
}

ll gcd(ll a,ll b)
{
    while(a!=b)
    {
        if(a>b)
            a-=b;
        else
            b-=a;
    }
    return a;
}


int main()
{
    ll m,n,q;
    char t;
    printf("============================================================================\n================================ | WELCOME | ===============================\n============================================================================\n");
    printf("1 | Type 'F/f' and press enter for Calculating factorial\n2 | Type 'P/p' and press enter to check if the number is prime\n3 | Type 'G/g' and press enter for Calculating GCD of 2 numbers\n");
    printf("5 | Type anything and press enter to exit\n============================================================================\n");
    while(1)
    {
        scanf("%c",&t);
        if(t=='F' || t=='f')
        {
            printf("Give a input for Calculating Factorial\n");
            scanf("%lld",&n);
            printf("Factorial Of %lld is : %lld\n",n,fact(n));
        }
        else if(t=='P' || t=='p')
        {
            printf("Give a input for checking If it is prime\n");
            scanf("%lld",&n);
            if(prime(n))
                printf("%lld Is a Prime Number\n",n);
            else
                printf("%lld is not a Prime number\n",n);
        }
        else if(t=='G' || t=='g')
        {
            printf("Give 2 inputs for both numbers\n");
            scanf("%lld %lld",&n,&m);
            printf("GCD of %lld %lld is : %lld\n",n,m,gcd(n,m));
        }
        else
        {
            printf("HAPPY CODING :)\n");
            break;
        }
        getchar();
    }
}