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简单DP，记忆化会RE，递推即可。

# include <cstdio>

# include <cstring>



# define N 100005



int n, t, f[N][11], a[N][11];

int Max(int x, int y){return x>y ? x:y;}

/*int dp(int x, int y)

{

    int &ans = f[x][y];

    if (ans >= 0) return ans;

    if (x > t) return ans = 0;

    ans = 0;

    ans = Max(ans, dp(x+1, y));

    if (y > 0) ans = Max(ans, dp(x+1, y-1));

    if (y < 10) ans = Max(ans , dp(x+1, y+1));

    return ans += a[x][y];

}*/

int main()

{

    int x, y, i, j;

    while (scanf("%d", &n), n)

    {

        t = 0;

        memset(f, 0, sizeof(f));

        memset(a, 0, sizeof(a));

        while (n--)

        {

            scanf("%d%d", &x, &y);

            ++a[y][x];

            if (y > t) t = y;

        }

        for (i = t; i >= 0; --i)

        for (j = 0; j < 11; ++j)

        {

            f[i][j] = f[i+1][j];

            if (j > 0) f[i][j] = Max(f[i+1][j-1], f[i][j]);

            if (j < 10) f[i][j] = Max(f[i+1][j+1], f[i][j]);

            f[i][j] += a[i][j];

        }

        printf("%d\n", f[0][5]);

    }

    

    return 0;

}