8611 大牛之路I

#include<stdio.h>
int a[];
int main()
{
    int i, n, m, sum, x, y;
    scanf("%d%d", &n, &m);
        for(i=; i<n; ++i)
        a[i] = i;
        for(i=; i<=m; ++i)
        {
            scanf("%d%d", &x, &y);
            a[y]=x;
        }
    for(sum=, i=; i<n; ++i)
        if(a[i] == i) ++sum;
        printf("%d\n", sum);
}