{"raw_statement":[{"iden":"problem statement","content":"We have $N$ sticks with negligible thickness. The length of the $i$\\-th stick is $A_i$.\nSnuke wants to select four different sticks from these sticks and form a rectangle (including a square), using the sticks as its sides. Find the maximum possible area of the rectangle."},{"iden":"constraints","content":"*   $4 \\leq N \\leq 10^5$\n*   $1 \\leq A_i \\leq 10^9$\n*   $A_i$ is an integer."},{"iden":"input","content":"Input is given from Standard Input in the following format:\n\n$N$\n$A_1$ $A_2$ ... $A_N$"},{"iden":"sample input 1","content":"6\n3 1 2 4 2 1"},{"iden":"sample output 1","content":"2\n\n$1 \\times 2$ rectangle can be formed."},{"iden":"sample input 2","content":"4\n1 2 3 4"},{"iden":"sample output 2","content":"0\n\nNo rectangle can be formed."},{"iden":"sample input 3","content":"10\n3 3 3 3 4 4 4 5 5 5"},{"iden":"sample output 3","content":"20"}],"translated_statement":null,"sample_group":[],"show_order":["default"],"formal_statement":null,"simple_statement":null,"has_page_source":true}