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long long find(int x,int y){    long long res=0;    int l1=level[x];    int l2=level[y];    int p1=x,p2=y;    if(l1<l2){        while(l2>l1){            p2=graph[p2];            l2=level[p2];        }        }    else if(l1>l2){        while(l1>l2){            p1=graph[p1];            l1=level[p1];        }        }      while(p1!=p2){        p2=graph[p2];        p1=graph[p1];    }    return p1;}