I've seen there are many WA's for this problem, even if you only need basic knowledge to solve it. Although i find my source perfect, i cannot imagine what makes it receive Wrong Answer on test #3

#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

#define MAXN 101

typedef struct shit
{
    int x, y;
};

shit a[MAXN];
int N, i, j;
int m[MAXN];

int cmp(shit a, shit b)
{
    return a.x < b.x ? 1 : 0;
}


int main(void)
{
    scanf("%d\n", &N);
    for (i = 0; i < N; i ++)
        scanf("%d %d\n", &(a[i].x), &(a[i].y));
    sort(a, a + N, cmp);

    int ans = 1;
    m[0] = 1;
    for (i = 1; i < N; i ++)
    {
        m[i] = 1;
        for (j = 0; j < i; j ++)
            if (a[j].y < a[i].y && 1 + m[j] > m[i])
                m[i] = 1 + m[j];

        if (m[i] > ans) ans = m[i];
    }

    printf("%d\n", N - ans);

    return 0;
}