int max(int a,int b)
{
    if ( a > b )
    return a;
    return b;
}
int pickingNumbers(int a_size, int* a) {
    int *countFrequence=calloc(100,sizeof(int));
    int i;
    int maximum=0;

    for ( i=0 ; i < a_size ; i++)
        ++countFrequence[a[i]];
    for ( i=1 ; i < 99 ; i++)
    maximum = max (maximum, countFrequence[i]+countFrequence[i+1]);
    return maximum;
}