here is my code

#include<stdio.h>

int main()
{

    int n,k,i,m,l,p=0,a[100001];
    scanf("%d",&n);
    for(i=0;i<n;i++)
    {
    scanf("%d",&k); a[k]++;
    }

    scanf("%d",&m);
    for(i=0;i<m;i++)
    {
    scanf("%d",&k); a[k]++;
    }

    scanf("%d",&l);
    for(i=0;i<l;i++)
    {
    scanf("%d",&k); a[k]++;
    if(a[k]==3){p++;}
    }


    printf("%d",p);


    return 0;}

Try a[1000000000+1], because k<=10^9.
But in this case you have not enuf memory, so try another method.

Edited by author 05.10.2012 15:20