robs CAOS 3 codechef

//gets wrong answer.

package main

import (
    "fmt"
)

var m [20]string
var monsters [20][20]bool
var cache [21][21][21][21]int
var cache_level [21][21][21][21]int
var level = 0

func main() {
    var T int
    fmt.Scan(&T)
    for ; T > 0; T-- {
        level++
        var R, C int
        fmt.Scan(&R)
        fmt.Scanf("%d\n", &C)
        for i := 0; i < R; i++ {
            fmt.Scanln(&m[i])
        }
        solve(R, C)
    }
}


func solve(R, C int) {
    for i := 0; i < 20; i++ {
        for j := 0; j < 20; j++ {
            monsters[i][j] = false
        }
    }
    find_monsters(R, C)

    if win(0, 0, R, C) != 0 {
        fmt.Println("Asuna")
    } else {
        fmt.Println("Kirito")
    }
}

func win(i1, j1, i2, j2 int) int {
    if cache_level[i1][j1][i2][j2] == level {
        return cache[i1][j1][i2][j2]
    }
    grundy_numbers := make(map[int]bool)
    for i := i1; i < i2; i++ {
        for j := j1; j < j2; j++ {
            if monsters[i][j] {
                game1 := win(i1, j1, i, j)
                game2 := win(i1, j + 1, i, j2)
                game3 := win(i + 1, j1, i2, j)
                game4 := win(i + 1, j + 1, i2, j2)
                grundy := game1 ^ game2 ^ game3 ^ game4
                grundy_numbers[grundy] = true
            }
        }
    }
    mex := 0
    for grundy_numbers[mex] {
        mex++
    }
    cache_level[i1][j1][i2][j2] = level
    cache[i1][j1][i2][j2] = mex
    return mex
}

func find_monsters(R, C int) {
    for i := 2; i + 2 < R; i++ {
        for j := 2; j + 2 < C; j++ {
            ok := true
            for dx := -2; dx <= 2; dx++ {
                if (m[i+dx][j] == '#') || (m[i][j+dx] == '#') {
                    ok = false
                }
            }
            if ok {
                monsters[i][j] = true
            }
        }
    }
}