//also use arr.reverse
function processData(input) {
let new_arr =[]
let res = 0
let string = input.split('\n');
let n = string[0]
let ar = string[1].split(" ").map(Number)
const arr = new Set(ar);
arr.forEach( a => new_arr.push(ar.count(a)))
new_arr.forEach( a => res += Math.floor(a/2) )
console.log(res)
// console.log(Math.floor(3/2))
}
Array.prototype.count = function(value) {
let count = 0;
this.forEach(item => {
if (item === value) {
count++;
}
});
return count;
}
process.stdin.resume();
process.stdin.setEncoding("ascii");
_input = "";
process.stdin.on("data", function (input) {
_input += input;
});
process.stdin.on("end", function () {
processData(_input);
});
