【模板】树状数组

//          可引入二维！！！！  </span>

int n;

int tree[MAXN];
inline int lowbit(int x)
{return x&(-x);}

int add(int a,int v)
{
for(int i=x;i<=n;i+=lowbit(i))
tree[i]+=v;
}
[ SUM(a,b)=sum(b)-sum(a); ]
[ sum(x); ]
int sum(int x)
{
int ans=0;
for(int i=x;i;i-=lowbit(i))
ans+=tree[i];
return ans;
}