import java.util.*;

class JY_150369 {

public long solution(int cap, int n, int[] deliveries, int[] pickups) {

long answer = 0;

int i = n-1;

while(i >= 0) {

System.out.println("i: "+i);

System.out.println("d: "+Arrays.toString(deliveries));

System.out.println("p: "+Arrays.toString(pickups));

// 배달과 수거 모두 끝난 집은 pass

if(deliveries[i] ==0 && pickups[i] ==0){

i--;

continue;

}

// 현재 가장 먼 집위치

int start = i+1;

// 배달하기

int capD = cap;

int d = i;

while(d >= 0) {

if(capD < deliveries[d]) {

deliveries[d] -= capD;

break;

}

capD -= deliveries[d];

deliveries[d] = 0;

d--;

}

// 수거하기

int capP = cap;

int p = i;

while(p >= 0) {

if(capP < pickups[p]) {

pickups[p] -= capP;

break;

}

capP -= pickups[p];

pickups[p] = 0;

p--;

}

answer += (start*2);

}

return answer;

}

}