#include <stdio.h>

int main() {
    int n, m, i, j, k, x, y, row,col, vys=0;
    scanf("%d %d", &n, &m);

    bool a[n][n];

    for (i = 0; i<n; i++)
        for (j = 0; j<n; j++)
            a[i][j] = false;

    for (i=0; i<m; i++) {
        scanf("%d %d", &x, &y);
        a[x-1][y-1] = true;
    }

    for (i = 0; i<n; i++) {
        for (j = 0; j<n; j++) {
            if (a[i][j] == true) {
                row = 0;
                col = 0;
                for(k=0; k<n; k++) {
                    row += (int)a[i][k];
                    col += (int)a[k][j];
                }
                if (row > 1 && col > 1) vys++;
            }
        }
    }
    int flagrow=1, flagcol=1;
    for (i = 0; i<n; i++) {
        row = 0;
        col = 0;
        for (k = 0; k<n; k++) {
            row += (int)a[i][k];
            col += (int)a[k][i];
        }
        if (row == 0) flagrow = 0;
        if (col == 0) flagcol = 0;
    }

    if (flagrow || flagcol) vys+=1;
    printf("%d", vys);


    return 0;
}