package main import ( "bufio" "errors" "fmt" "io" "os" "strconv" ) /*********** I/O ***********/ var ( // ReadString returns a WORD string. ReadString func() string stdout *bufio.Writer ) func init() { ReadString = newReadString(os.Stdin) stdout = bufio.NewWriter(os.Stdout) } func newReadString(ior io.Reader) func() string { r := bufio.NewScanner(ior) r.Buffer(make([]byte, 1024), int(1e+11)) // Split sets the split function for the Scanner. The default split function is ScanLines. // Split panics if it is called after scanning has started. r.Split(bufio.ScanWords) return func() string { if !r.Scan() { panic("Scan failed") } return r.Text() } } // ReadInt returns an integer. func ReadInt() int { return int(readInt64()) } func readInt64() int64 { i, err := strconv.ParseInt(ReadString(), 0, 64) if err != nil { panic(err.Error()) } return i } // ReadIntSlice returns an integer slice that has n integers. func ReadIntSlice(n int) []int { b := make([]int, n) for i := 0; i < n; i++ { b[i] = ReadInt() } return b } // ReadFloat64 returns an float64. func ReadFloat64() float64 { return float64(readFloat64()) } func readFloat64() float64 { f, err := strconv.ParseFloat(ReadString(), 64) if err != nil { panic(err.Error()) } return f } // ReadFloatSlice returns an float64 slice that has n float64. func ReadFloat64Slice(n int) []float64 { b := make([]float64, n) for i := 0; i < n; i++ { b[i] = ReadFloat64() } return b } // ReadRuneSlice returns a rune slice. func ReadRuneSlice() []rune { return []rune(ReadString()) } /*********** Debugging ***********/ // ZeroPaddingRuneSlice returns binary expressions of integer n with zero padding. // For debugging use. func ZeroPaddingRuneSlice(n, digitsNum int) []rune { sn := fmt.Sprintf("%b", n) residualLength := digitsNum - len(sn) if residualLength <= 0 { return []rune(sn) } zeros := make([]rune, residualLength) for i := 0; i < len(zeros); i++ { zeros[i] = '0' } res := []rune{} res = append(res, zeros...) res = append(res, []rune(sn)...) return res } /*********** DP sub-functions ***********/ // ChMin accepts a pointer of integer and a target value. // If target value is SMALLER than the first argument, // then the first argument will be updated by the second argument. func ChMin(updatedValue *int, target int) bool { if *updatedValue > target { *updatedValue = target return true } return false } // ChMax accepts a pointer of integer and a target value. // If target value is LARGER than the first argument, // then the first argument will be updated by the second argument. func ChMax(updatedValue *int, target int) bool { if *updatedValue < target { *updatedValue = target return true } return false } // NthBit returns nth bit value of an argument. // n starts from 0. func NthBit(num, nth int) int { return num >> uint(nth) & 1 } /*********** Arithmetic ***********/ // Max returns the max integer among input set. // This function needs at least 1 argument (no argument causes panic). func Max(integers ...int) int { m := integers[0] for i, integer := range integers { if i == 0 { continue } if m < integer { m = integer } } return m } // Min returns the min integer among input set. // This function needs at least 1 argument (no argument causes panic). func Min(integers ...int) int { m := integers[0] for i, integer := range integers { if i == 0 { continue } if m > integer { m = integer } } return m } // DigitSum returns digit sum of a decimal number. // DigitSum only accept a positive integer. func DigitSum(n int) int { if n < 0 { return -1 } res := 0 for n > 0 { res += n % 10 n /= 10 } return res } // Sum returns multiple integers sum. func Sum(integers ...int) int { s := 0 for _, i := range integers { s += i } return s } // CeilInt returns the minimum integer larger than or equal to float(a/b). func CeilInt(a, b int) int { res := a / b if a%b > 0 { res++ } return res } // FloorInt returns the maximum integer smaller than or equal to float(a/b) func FloorInt(a, b int) int { res := a / b return res } // PowInt is integer version of math.Pow // PowInt calculate a power by Binary Power (二分累乗法(O(log e))). func PowInt(a, e int) int { if a < 0 || e < 0 { panic(errors.New("[argument error]: PowInt does not accept negative integers")) } if e == 0 { return 1 } if e%2 == 0 { halfE := e / 2 half := PowInt(a, halfE) return half * half } return a * PowInt(a, e-1) } // AbsInt is integer version of math.Abs func AbsInt(a int) int { if a < 0 { return -a } return a } // Gcd returns the Greatest Common Divisor of two natural numbers. // Gcd only accepts two natural numbers (a, b >= 1). // 0 or negative number causes panic. // Gcd uses the Euclidean Algorithm. func Gcd(a, b int) int { if a <= 0 || b <= 0 { panic(errors.New("[argument error]: Gcd only accepts two NATURAL numbers")) } if a < b { a, b = b, a } // Euclidean Algorithm for b > 0 { div := a % b a, b = b, div } return a } // Lcm returns the Least Common Multiple of two natural numbers. // Lcd only accepts two natural numbers (a, b >= 1). // 0 or negative number causes panic. // Lcd uses the Euclidean Algorithm indirectly. func Lcm(a, b int) int { if a <= 0 || b <= 0 { panic(errors.New("[argument error]: Gcd only accepts two NATURAL numbers")) } // a = a'*gcd, b = b'*gcd, a*b = a'*b'*gcd^2 // a' and b' are relatively prime numbers // gcd consists of prime numbers, that are included in a and b gcd := Gcd(a, b) // not (a * b / gcd), because of reducing a probability of overflow return (a / gcd) * b } // Strtoi is a wrapper of `strconv.Atoi()`. // If `strconv.Atoi()` returns an error, Strtoi calls panic. func Strtoi(s string) int { if i, err := strconv.Atoi(s); err != nil { panic(errors.New("[argument error]: Strtoi only accepts integer string")) } else { return i } } // PrintIntsLine returns integers string delimited by a space. func PrintIntsLine(A ...int) string { res := []rune{} for i := 0; i < len(A); i++ { str := strconv.Itoa(A[i]) res = append(res, []rune(str)...) if i != len(A)-1 { res = append(res, ' ') } } return string(res) } /********** I/O usage **********/ //str := ReadString() //i := ReadInt() //X := ReadIntSlice(n) //S := ReadRuneSlice() /*******************************************************************/ const MOD = 1000000000 + 7 const ALPHABET_NUM = 26 var n int var A, B []int var dp [1 << 18][18]int func main() { n = ReadInt() A, B = make([]int, n), make([]int, n) for i := 0; i < n; i++ { A[i], B[i] = ReadInt(), ReadInt() } if n == 1 { fmt.Println(0) return } for S := 0; S < (1 << uint(n)); S++ { for j := 0; j < n; j++ { dp[S][j] = 1 << 60 } } for S := 0; S < (1 << uint(n)); S++ { for j := 0; j < n; j++ { for k := 0; k < n; k++ { if S == 0 { dp[S|1<