Go: package main

import (
	"bufio"
	"fmt"
	"math"
	"os"
	"strconv"
)

type Matrix struct {
	r int // num of row
	c int // num of column
}

type Range struct {
	start int // index, inclusive
	end   int // index, inclusive
}

func (r Range) length() int {
	return r.end - r.start + 1
}

func calcMultiplication(x, y Matrix) (Matrix, int) {
	if x.c != y.r {
		panic("cannnot calculate")
	}
	return Matrix{x.r, y.c}, x.r * y.c * x.c
}

func calcMinMatrixChainMultiplication(matrices []Matrix, r Range, memo map[Range]int) (Matrix, int) {
	if v, ok := memo[r]; ok {
		return Matrix{matrices[r.start].r, matrices[r.end].c}, v
	}
	if r.length() == 0 {
		panic("must not be empty")
	} else if r.length() == 1 {
		return matrices[r.start], 0
	}

	var minCount int = math.MaxInt32

	for i := 0; i < r.length()-1; i++ {
		formerRange := Range{r.start, r.start + i}
		latterRange := Range{r.start + i + 1, r.end}
		matF, countF := calcMinMatrixChainMultiplication(matrices, formerRange, memo)
		matL, countL := calcMinMatrixChainMultiplication(matrices, latterRange, memo)
		_, countFL := calcMultiplication(matF, matL)
		count := countF + countL + countFL
		if count < minCount {
			minCount = count
		}
	}
	memo[r] = minCount
	return Matrix{matrices[r.start].r, matrices[r.end].c}, minCount
}

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	n, _ := nextInt(sc)
	matrices := make([]Matrix, n)
	for i := 0; i < n; i++ {
		r, _ := nextInt(sc)
		c, _ := nextInt(sc)
		matrices[i] = Matrix{r, c}
	}
	memo := make(map[Range]int)
	_, resultCount := calcMinMatrixChainMultiplication(matrices, Range{0, len(matrices) - 1}, memo)
	fmt.Println(resultCount)
}

func nextInt(sc *bufio.Scanner) (int, error) {
	sc.Scan()
	return strconv.Atoi(sc.Text())
}

C++: #include<iostream>
#include<algorithm>
using namespace std;

#define INF (100 * 100 * 100 * 100)

int n, m[110][110];

void matrixChainOrder(int *p){
  for(int i = 1;i <= n;i++) m[i][i] = 0;
  
  for(int l = 2;l <= n;l++){
    for(int i = 1;i <= n - l + 1;i++){
      int j = i + l - 1;
      m[i][j] = INF;
      for(int k = i;k <= j - 1;k++){
        int q = m[i][k] + m[k + 1][j] + p[i - 1] * p[k] * p[j];
        m[i][j] = min(m[i][j], q);
      }
    }
  }
}

int main(){
  
  int p[110];
  
  cin >> n;
  
  for(int i = 0;i < n;i++){
    int r, c;
    
    cin >> r >> c;
    if(i) p[i + 1] = c;
    else{
      p[0] = r;
      p[1] = c;
    }
  }
  
  matrixChainOrder(p);
  
  cout << m[1][n] << endl;
  
  return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <climits>

using namespace std;

static const int N = 100;
static int m[N + 1][N + 1] = {}, p[N + 1] = {};

static inline void matrixChainMultiplication(int n) {
  for (int l = 2; l <= n; l++) {
    for (int i = 1; i <= n - l + 1; i++) {
      int j = i + l - 1;
      m[i][j] = INT_MAX;
      for (int k = i; k <= j - 1; k++) {
        m[i][j] = min(m[i][j], m[i][k] + m[k + 1][j] + p[i - 1] * p[k] * p[j]); 
      }
    }
  }
}

int main() {
  int n;
  cin >> n;
  
  for (int i = 1; i <= n; i++) {
    cin >> p[i - 1] >> p[i];
  }

  matrixChainMultiplication(n);
  
  cout << m[1][n] << endl;

  return 0;
}

C++: #include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)n;i++)
#define ll long long
using namespace std;

static const int N=100;

int main(){
    int n,p[N+1],m[N+1][N+1];
    cin>>n;
    for (int i=1;i<=n;i++) cin>>p[i-1]>>p[i];
    for (int i=1;i<=n;i++) m[i][i]=0;
    for (int l=2;l<=n;l++) {
        for (int i=1;i<=n-l+1;i++){
            int j=i+l-1;//長さ
            m[i][j]=(1<<21);
            for (int k=i;k<=j-1;k++){
                m[i][j]=min(m[i][j],m[i][k]+m[k+1][j]+p[i-1]*p[k]*p[j]);
            }
        }
    }

    cout<<m[1][n]<<endl;

    return 0;
}

C++: #include <iostream>
#include <algorithm>
using namespace std;

static const int N = 100;

int main()
{
    int n, p[N + 1], m[N + 1][n + 1];
    cin >> n;
    for (int i = 1; i <= n; i++)
    {
        cin >> p[i - 1] >> p[i];
    }

    for (int i = 1; i <= n; i++)
        m[i][i] = 0;
    for (int l = 2; l <= n; l++)
    {
        for (int i = 1; i <= n - l + 1; i++)
        {
            int j = i + l - 1;
            m[i][j] = (1 << 21);
            for (int k = i; k <= j - 1; k++)
            {
                m[i][j] = min(m[i][j], m[i][k] + m[k + 1][j] + p[i - 1] * p[k] * p[j]);
            }
        }
    }

    cout << m[1][n] << endl;

    return 0;
}

C++: // ALDS1_10_B Matrix Chain Multiplication
#include <iostream>
#include <vector>
#include <algorithm>
#include <utility>
#define INF 900000000
bool debug = false;
std::vector<std::vector<int>> dp;

void MatrixChainMultiplication(std::vector<std::pair<int,int>> sequence) {
    dp.resize(sequence.size());
    for (int i=0; i<dp.size(); i++) dp.at(i).resize(sequence.size());

    /*
    example:
        aN is a matrix. 
        ... a3 (a4 a5 a6)*(a7 a8) a9 ...
        i = 5, j = 4, k = 3
    */

    /* i = length of set */
    for (int i=2; i<dp.size(); i++) {
        /* j = front point */
        for (int j=1; j<=dp.at(i).size()-i; j++) {
            /* initialization of dp.at(i).at(j) */
            dp.at(i).at(j) = INF;
            /* k = dividing point */
            for (int k=1; k<i; k++) {
                if (i == 2) {
                    dp.at(i).at(j) = sequence.at(j).first*sequence.at(j).second*sequence.at(j+1).second;
                } else {
                    dp.at(i).at(j) = std::min(dp.at(i).at(j),
                                              dp.at(k).at(j)+dp.at(i-k).at(j+k)+sequence.at(j).first*sequence.at(j+k-1).second*sequence.at(i+j-1).second);
                    
                }
            }
            if (debug) {
                std::cout << "dp.at(" << i << ").at(" << j << ") = " << dp.at(i).at(j) << ":";
                for (int n=j; n<i+j; n++) std::cout << " " << n;
                std::cout << "\n";
            }
        }
    }
    std::cout << dp.back().at(1) << "\n";
}

int main() {
    int total; std::cin >> total;
    std::vector<std::pair<int,int>> sequence;
    sequence.resize(total+1);
    for (int i=1; i<sequence.size(); i++) {
        std::cin >> sequence.at(i).first >> sequence.at(i).second;
    }
    MatrixChainMultiplication(sequence);
}

C++: #include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (n); ++i)
using namespace std;
typedef float fl;
typedef long long ll;

static const int N = 100;

int main(){
    int n, p[N + 1], m[N + 1][N + 1];
    cin >> n;
    for(int i = 1; i <= n; i++) cin >> p[i - 1] >> p[i];

    for(int i = 1; i <= n; i++) m[i][i] = 0;
    for(int l = 2; l <= n; l++){
        for(int i = 1; i <= n - l + 1; i++){
            int j = i + l - 1;
            m[i][j] = (1 << 21);
            for(int k = i; k <= j - 1; k++){
                m[i][j] = min(m[i][j], m[i][k] + m[k + 1][j] + p[i - 1]*p[k]*p[j]);
            }
        }
    }
    cout << m[1][n] << endl;
    return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
#define r(i,n) for(auto i=0;i<n;i++)
#define s(c) static_cast<int>((c).size())

int main(){
	int n;
	cin >> n;
	int i, t, A[n+1];
	cin >> A[0] >> A[1];
	for(i = 2; i <= n; i++){
		cin >> t >> A[i];
	}

	//dp[l][r] -> min(A[l]*...*A[r])
	int dp[n][n+1]{}, dplr, l, r;
	for(int i = 1; i <= n; i++){
		for(int j = 0; j < n-i; j++){
			l = j;
			r = j+i;
			dplr = INT_MAX;
			for(int k = l; k < r; k++){
				dplr = min(dplr, dp[l][k] + dp[k+1][r] + A[l]*A[k+1]*A[r+1]);
			}
			dp[l][r] = dplr;
			//printf("[%d, %d]=%d ", l, r, dplr);
		}
		//printf("\n");
	}

	printf("%d\n", dp[0][n-1]);
}

C++: #include<bits/stdc++.h>
using namespace std;
main(){
  int a[44],n;
  a[0]=a[1]=1;
  cin>>n;
  for(int i=2;i<=n;i++)a[i]=a[i-1]+a[i-2];
  cout<<a[n]<<endl; 
}