package main import ( "bufio" "fmt" "os" "strconv" ) func configure(scanner *bufio.Scanner) { scanner.Split(bufio.ScanWords) scanner.Buffer(make([]byte, 1000005), 1000005) } func getNextString(scanner *bufio.Scanner) string { scanned := scanner.Scan() if !scanned { panic("scan failed") } return scanner.Text() } func getNextInt(scanner *bufio.Scanner) int { i, _ := strconv.Atoi(getNextString(scanner)) return i } func getNextInt64(scanner *bufio.Scanner) int64 { i, _ := strconv.ParseInt(getNextString(scanner), 10, 64) return i } func getNextFloat64(scanner *bufio.Scanner) float64 { i, _ := strconv.ParseFloat(getNextString(scanner), 64) return i } func main() { fp := os.Stdin wfp := os.Stdout extra := 0 if os.Getenv("I") == "IronMan" { fp, _ = os.Open(os.Getenv("END_GAME")) extra = 100 } scanner := bufio.NewScanner(fp) configure(scanner) writer := bufio.NewWriter(wfp) defer func() { r := recover() if r != nil { fmt.Fprintln(writer, r) } writer.Flush() }() solve(scanner, writer) for i := 0; i < extra; i++ { fmt.Fprintln(writer, "-----------------------------------") solve(scanner, writer) } } func solve(scanner *bufio.Scanner, writer *bufio.Writer) { n := getNextInt(scanner) m := getNextInt(scanner) ee := makeGrid(n, n) for i := 0; i < m; i++ { a := getNextInt(scanner) b := getNextInt(scanner) ee[a][b] = 1 ee[b][a] = 1 } var ans int for i := 0; i < n; i++ { for j := 0; j < i; j++ { for k := 0; k < j; k++ { for l := 0; l < k; l++ { if square(i, j, k, l, ee) { ans++ } } } } } fmt.Fprintln(writer, ans) } func square(i, j, k, l int, ee [][]int) bool { m := map[int]int{} m[i] += ee[i][j] m[i] += ee[i][k] m[i] += ee[i][l] m[j] += ee[j][i] m[j] += ee[j][k] m[j] += ee[j][l] m[k] += ee[k][j] m[k] += ee[k][i] m[k] += ee[k][l] m[l] += ee[l][j] m[l] += ee[l][k] m[l] += ee[l][i] for _, c := range m { if c != 2 { return false } } return true } func makeGrid(h, w int) [][]int { index := make([][]int, h, h) data := make([]int, h*w, h*w) for i := 0; i < h; i++ { index[i] = data[i*w : (i+1)*w] } return index }