Spoj brackets segment tree - segment-tree

Question

can anyone help me in my code. I am getting WA and m not able to rectify it plzzz
my code http://ideone.com/DkrwIg
problem link : http://www.spoj.com/problems/BRCKTS/
i am a bit doubtful in my modification function.
#include<iostream>
#include<cstdio>
#include<cstdlib>
using namespace std;
char str[40010];
struct node
{
int sum;
int minsum;
}tree[1000005];
void build(int id,int l,int r)
{
if(r-l<2)
{
if(str[l] == '(')
{
tree[id].sum = 1;
tree[id].minsum = 1;
}
else
{
tree[id].sum = -1;
tree[id].minsum = -1;
}
return;
}
int mid = (r+l)/2;
build(id*2,l,mid);
build(id*2+1,mid,r);
tree[id].sum = tree[id*2].sum + tree[id*2+1].sum;
tree[id].minsum = min(tree[id*2].minsum,tree[id*2].minsum+tree[id*2+1].minsum);
}
void modify(int index,int id,int l,int r)
{
if(r-l<2)
{
tree[id].sum = tree[id].minsum = -tree[id].sum;
return;
}
int mid = (r+l)/2;
if(index<mid)
modify(index,id*2,l,mid);
else
modify(index,id*2+1,mid,r);
tree[id].sum = tree[id*2].sum + tree[id*2+1].sum;
tree[id].minsum = min(tree[id*2].minsum,tree[id*2].minsum+tree[id*2+1].minsum);
}
int main()
{
int n,k;
int val;
int h = 1;
for(int h=1;h<=10;h++)
{
scanf("%d",&n);
scanf("%s",str);
build(1,0,n);
//cout<<"Test "<<h<<" :"<<endl;
printf("Test %d:\n",h);
//cin>>k;
scanf("%d",&k);
while(k--)
{
cin>>val;
if(!val)
{
if(tree[1].sum == 0 && tree[1].minsum == 0)
{
//cout<<"YES"<<endl;
printf("YES\n");
}
else
{
//cout<<"NO"<<endl;
printf("NO\n");
}
//cout<<tree[1].sum<<"------------"<<tree[1].minsum<<endl;
}
else
{
modify(val-1,1,0,n);
}
}
}
return 0;
}