stack problem 1

#include<stdio.h>
#include<stdlib.h>
int stack[100],top=-1,flag=0;
void push(int x)
{
    if(top==99 || top>99){
        printf("stack overflow\n");
    }
    else stack[++top]=x;
}

int pop()
{
    if(top<0){
        flag++;
        return 0;
    }
    else{
        return stack[top--];
    }
}
int main()
{
    int n,i,x;
    for(i=1;i<3;i++)
    {
        printf("Number of data: ");
        scanf("%d",&n);
        printf("\n");
        while(n--){
            scanf("%d",&x);
            push(x);
        }
        printf("how many data to display: ");
        scanf("%d",&n);
        printf("\n");
        while(n--){
            x=pop();
            if(flag==0){
            printf("Data = %d\n",x);
            }
            else{
                printf("Stack is empty\n");
            }
        }
        top=-1;
    }
}