C++ :

#include <cstdio>
int main(){
    int n, m;
    if(scanf("%d %d", &n, &m) != 2) return 0;
    int x1, y1, x2, y2;
    if(scanf("%d %d %d %d", &x1, &y1, &x2, &y2) != 4) return 0;
    if(x1 > x2){ int t = x1; x1 = x2; x2 = t; }
    if(y1 > y2){ int t = y1; y1 = y2; y2 = t; }
    /* A(1,1) -> B(n,m)，只能向东(+x)或向北(+y)。障碍矩形 [x1..x2]x[y1..y2] 不可通行。 */
    static long long f[64][64];
    for(int i=1;i<=n;i++) for(int j=1;j<=m;j++){
        if(i >= x1 && i <= x2 && j >= y1 && j <= y2){ f[i][j] = 0; continue; }
        if(i == 1 && j == 1){ f[i][j] = 1; continue; }
        f[i][j] = 0;
        if(i > 1) f[i][j] += f[i-1][j];
        if(j > 1) f[i][j] += f[i][j-1];
    }
    printf("%lld\n", f[n][m]);
    return 0;
}