include

int main() { int n, k; scanf("%d %d", &n, &k);

int bill[n];
int total = 0;

// Input bill item
for(int i = 0; i < n; i++) {
    scanf("%d", &bill[i]);
    total += bill[i];
}

int b;
scanf("%d", &b);

// Calculate Anna's actual share
int anna_share = (total - bill[k]) / 2;

if(anna_share == b) {
    printf("Bon Appetit");
} else {
    printf("%d", b - anna_share);
}

return 0;

}

Python 3 Solution:

def sockMerchant(n, ar):
    dic_stocks = {}
    count = 0
    for x in ar:
        if x in dic_stocks:
            dic_stocks[x] += 1 
        else:
            dic_stocks[x] = 1
    for x in dic_stocks:
        count += dic_stocks[x] // 2
    return count

The pythonic way: (not the best solution but it works)

def sockMerchant(n,ar):
    count = {num:ar.count(num) for num in ar}
    pairs = [int((val/2)) for num,val in count.items()]
    return sum(pairs)

def sockMerchant(n, ar): d = Counter(ar) pairs = 0 for value in d.values(): pairs += math.floor(value/2) return pairs bmw spare parts

For Ruby

ar.tally.map {|_, v| v/2}.sum