cf984e Elevator

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#include <iostream>
#include <cstring>
#include <cstdio>
#include <cmath>
using namespace std;
int n, u[2005], v[2005], f[2005][11][11][11][11];
int dis(int x, int y){
	return abs(x-y);
}
int dfs(int i, int cur, int a, int b, int c){
	if(f[i][cur][a][b][c]!=-1)	return f[i][cur][a][b][c];
	int re = 0x3f3f3f3f;
	if(i>n){
		if(!a && !b && !c)	return 0;
		if(a)	re = min(re, dfs(i, a, 0, b, c)+dis(cur,a)+1);
		if(b)	re = min(re, dfs(i, b, a, 0, c)+dis(cur,b)+1);
		if(c)	re = min(re, dfs(i, c, a, b, 0)+dis(cur,c)+1);
		f[i][cur][a][b][c] = re;
		return re;
	}
	if(a)	re = min(re, dfs(i, a, 0, b, c)+dis(cur,a)+1);
	if(b)	re = min(re, dfs(i, b, a, 0, c)+dis(cur,b)+1);
	if(c)	re = min(re, dfs(i, c, a, b, 0)+dis(cur,c)+1);
	if(a && b && c){
		re = min(re, dfs(i+1, v[i], a, b, c)+dis(cur,u[i])+dis(u[i],v[i])+2);
		re = min(re, dfs(i+1, a, v[i], b, c)+dis(cur,u[i])+dis(u[i],a)+2);
		re = min(re, dfs(i+1, b, a, v[i], c)+dis(cur,u[i])+dis(u[i],b)+2);
		re = min(re, dfs(i+1, c, a, b, v[i])+dis(cur,u[i])+dis(u[i],c)+2);
	}
	else{
		if(!a)	re = min(re, dfs(i+1, u[i], v[i], b, c)+dis(cur,u[i])+1);
		else if(!b)	re = min(re, dfs(i+1, u[i], a, v[i], c)+dis(cur,u[i])+1);
		else	re = min(re, dfs(i+1, u[i], a, b, v[i])+dis(cur,u[i])+1);
	}
	f[i][cur][a][b][c] = re;
	return re;
}
int main(){
	cin>>n;
	for(int i=1; i<=n; i++)
		scanf("%d %d", &u[i], &v[i]);
	memset(f, -1, sizeof(f));
	cout<<dfs(1, 1, 0, 0, 0)<<endl;
	return 0;
}