{"raw_statement":[{"iden":"problem statement","content":"You have $N$ socks. The color of the $i$\\-th sock is $A_i$.\nYou want to perform the following operation as many times as possible. How many times can it be performed at most?\n\n*   Choose two same-colored socks that are not paired yet, and pair them."},{"iden":"constraints","content":"*   $1\\leq N \\leq 5\\times 10^5$\n*   $1\\leq A_i \\leq 10^9$\n*   All values in the input are integers."},{"iden":"input","content":"The input is given from Standard Input in the following format:\n\n$N$\n$A_1$ $A_2$ $\\dots$ $A_N$"},{"iden":"sample input 1","content":"6\n4 1 7 4 1 4"},{"iden":"sample output 1","content":"2\n\nYou can do the operation twice as follows.\n\n*   Choose two socks with the color $1$ and pair them.\n*   Choose two socks with the color $4$ and pair them.\n\nThen, you will be left with one sock with the color $4$ and another with the color $7$, so you can no longer do the operation. There is no way to do the operation three or more times, so you should print $2$."},{"iden":"sample input 2","content":"1\n158260522"},{"iden":"sample output 2","content":"0"},{"iden":"sample input 3","content":"10\n295 2 29 295 29 2 29 295 2 29"},{"iden":"sample output 3","content":"4"}],"translated_statement":null,"sample_group":[],"show_order":["default"],"formal_statement":null,"simple_statement":null,"has_page_source":true}