Queue

#include<stdio.h>
int head=-1, tail=-1, arr[100];

void enqueue(int n)
{
    if(tail>=100)
    {
        printf("It's overflown.\n");
        return;
    }
    else if(head==-1 && tail==-1)
    {
        head=0;
        arr[++tail]=n;
        return;
    }
    else
        arr[++tail]=n;
}

int dequeue()
{
    if(head==-1)
    {
        printf("It's empty.\n");
        return -1;
    }
    else
    {
        int temp=arr[head];
        head++;
        if(head>tail)
        {
            head=-1;
            tail=-1;
        }
        return temp;
    }
}

int main()
{
    int i,n,x,y,a,b,sum=0;
    scanf("%d", &n);
    for(i=0; i<n; i++)
    {
        scanf("%d", &x);
        enqueue(x);
    }
    scanf("%d", &y);
    for(i=0; i<y; i++)
    {
        a=dequeue();
        sum=sum+a;
        printf("%d ", a);
    }
    printf("sum: %d\n", sum);
}