Removing negative values in Queue : C program

#include <stdio.h>
#include <stdlib.h>
#define MAX 10
int queue[MAX],f=-1,r=-1;
void enq();
void deq();
void display();
void deletenegative();
main()
{
int n,i;
printf("enter the number of elements");
scanf("%d",&n);
for(i=1;i<=n;i++)
enq();
display();
printf("\nAfter deleting negative values\n");
deletenegative();
display();
}
void enq()
{
int val;
if(r==MAX-1) {
printf("Queue full");
return;
}
else if(f == -1 && r == -1)
f=r=0;
else
r=r+1;
printf("enter the data to be entered\n");
scanf("%d",&val);
queue[r]=val;
}
void deq()
{
if(f==-1)
{
printf("underflow");
return;
}
if(f ==r)
f=r=-1;
else
f=f+1;
}

void display()
{
int i;
if(f ==-1)
printf("queue empty\n");
else
{
for(i=f; i<=r;i++)
    printf("%d\t",queue[i]);
}
}
void move(int i)
{
for( ;i<r;i++)
queue[i]=queue[i+1];

}
void deletenegative()
{
int i;
if(f ==-1)
printf("queue empty\n");
else
{
for(i=f; i<=r;)
{
if(queue[i] <0)
{
if(i==f)
{
deq();
i=i+1;
}
else
{
move(i);
r=r-1;
i=i-1;
}
}
else
i=i+1;
}
}
}