#include <cstdio>
int c[21][21];
int main() {
    c[1][1] = 1;
    int n, m, x, y;
    scanf("%d %d %d %d", &n, &m, &x, &y);
    int v[4][2] = {{n - 2, m - 1}, {n - 2, m + 1}, {n - 1, m - 2}, {n + 1, m-2}};
    for (int i = 0; i < 4; i++) {
        c[v[i][0]][v[i][1]] = -1;
    }
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            if (c[i][j] = -1) continue;
            c[i][j] = c[i-1][j] + c[i][j-1];
            if (c[i-1][j] == -1) c[i][j] ++;
            if (c[i][j-1] == -1) c[i][j] ++;
        }
    }
    printf("%d", c[n][m]);
    return 0;
}

用的动态规划，为啥wa了？ 球球大神指导。