树状数组

单点修改，区间查询

int lowbit(int x){return x&-x;}
int qu(int x){
    int an1=0;
    while(x){an1+=c[x];x-=lowbit(x);}
    return an1;
}
void add(int x,int y){while(x<=n){c[x]+=y;x+=lowbit(x);}}