Pair of Prime Numbers

For any even number n greater than or equal to 4, there exists at least one pair of prime numbers p1 and p2 such that n = p1 + p2.
Write a C program that finds the number of all pairs of prime numbers satisfying the condition n = p1 + p2 for a given even number(n).

Even number which is greater than or equal to 4 and less than 215 is given as input and number of pairs of prime number is the output.
[Note: Do not consider (p1, p2) and (p2, p1) separately as two different pairs.]

#include<stdio.h>
#include<math.h>
int isprime(int n){
    int i;
    if(n==1 ){
        return 0;
    }
    if(n==2) return 1;
    if(n%2==0) return 0;
    for(i=2;i<=n/2;i++){
        if(n%i==0) return 0;
    }
    return 1;
}
int main()
{
int i,n,cnt=0;
    printf("Enter the value\n");
    scanf("%d",&n);
    if(n%2!=0 || n<4 || n > pow(2,15)) printf("Invalid Input");
    else{
    for(i=n-1;i>=n/2;i--){
        if(isprime(i)){
            if(isprime(n-i)){
                cnt++;
            }
        }
    }
	printf("Number of pairs for %d is %d",n,cnt);
    }
	return 0;
}