int max_of_four(int a, int b, int c, int d){
    int max = 0;
    int arr[4] = {a,b,c,d};
    max = arr[0];
    for(int i = 0;i<4;++i){
        
        if(arr[i]>max){
            max = arr[i];
        }
    }
    return max;