An array of exercises (wrong version)

#include<stdio.h>
int main()
{
    int k, i, b, a, y, c, n;
    int num[i];
    int sum = 0, cont = 0;
    scanf("%d", &i);
    for(y = 0; y < i; y++){
        scanf("%d", &num[i]);
    }
    for(a = 0; a < i; a++){
        for(b = 0; b < i; b++){
            for(i = 0; i < 4; i++){
                n = num[a] + num[b];
                k = num[cont++]; 
                if(n == k && num[a] != num[b] ){
                sum++;                    
            }

        }
    }
}
    printf("%d", sum );
    return 0;
}