#include <stdio.h>

#include <stdlib.h>

#define maxs 5001

int dp[2][maxs][2];

#define INF 0x7ffffffe

#define f(i, j, k) ((j >= 0 && j < maxs) ? dp[i][j][k] : INF)

int min2(int a, int b) { return a < b ? a : b; }

int min4(int a, int b, int c, int d) {

return min2(min2(a, b), min2(c, d));

}

int main() {

for (int i = 0; i < 2 ;i++)

for (int j = 0; j < maxs; j++)

for(int k = 0; k < 2; k++) dp[i][j][k] = INF;

int cur = 0, pre = 1;

dp[pre][0][0] = dp[pre][0][1] = 0;

int n, a, b, s;

scanf("%d", &n);

for (int i = 1; i <= n; i++) {

scanf("%d %d", &a, &b);

for (int j = 0; j <= i * 5; j++) {

s = a - b;

dp[cur][j][0] = min4(f(pre, j - s, 0), f(pre, j + s, 0) + 1,

f(pre, s - j, 1), f(pre, - s - j, 1) + 1);

s = b - a;

dp[cur][j][1] = min4(f(pre, j - s, 1), f(pre, j + s, 1) + 1,

f(pre, s - j, 0), f(pre, - s - j, 0) + 1);

}

cur = cur + pre;

pre = cur - pre;

cur = cur - pre;

}

int ans;

for (int i = 0; i <= n * 5; i++)

if ((ans = min2(dp[pre][i][0], dp[pre][i][1])) < INF) {

printf("%d\n", ans);

break;

}

exit(0);

}