Probability that at least two events occur

Let $E_1, E_2$ and $E_3$ be three events such that $$P(E_1\cap E_2)=\frac{1}{4},\quad P(E_1\cap E_3)=P(E_2\cap E_3)=\frac{1}{5}\quad\text{and}\quad P(E_1\cap E_2\cap E_3)=\frac{1}{6}.$$ Then, among the events $E_1, E_2$ and $E_3$, the probability that at least two events occur, equals