Looking at this problem, I need to find the number of ways to move a token from cell n to cell 1.

Let me define `dp[i]` = number of ways to reach cell 1 from cell i.
- `dp[1] = 1`
- For `i > 1`: `dp[i] = sum of dp[j]` for all j reachable from i in one move.

From cell x, I can reach:
1. Any cell `x - y` where `1 <= y <= x-1`, meaning cells `1` to `x-1` (subtraction)
2. Cell `floor(x/z)` for `z` from `2` to `x` (floored division)

So `dp[x] = (sum of dp[1..x-1]) + (sum of dp[floor(x/z)] for z=2..x)`

Let `S[x] = dp[1] + dp[2] + ... + dp[x]`

Then the subtraction part gives `S[x-1]`.

For the division part, I need `sum of dp[floor(x/z)] for z=2..x`.

The values `floor(x/z)` take O(sqrt(x)) distinct values. For each distinct value `v = floor(x/z)`, it appears for a range of z values. The count of z values giving the same floor is the number of times that value appears.

Let me think differently. Let `f[x]` = contribution from division moves from cell x = sum over z=2 to x of dp[floor(x/z)].

For each value v = floor(x/z), v ranges from 1 to floor(x/2). For a given v, the number of z in [2,x] with floor(x/z) = v is (number of z with floor(x/z)=v).

Actually, let me compute f[x] using the fact that floor(x/z) takes O(sqrt(x)) distinct values.

So `dp[x] = S[x-1] + f[x]` where `f[x] = sum_{z=2}^{x} dp[floor(x/z)]`.

Memory concern: n up to 4*10^6, and we need dp array and prefix sum array. Two arrays of int32 = 2 * 4MB * 4 = 32MB. Should be fine if limit is around 64MB.

Let me implement this:

```go
package main

import (
    "bufio"
    "fmt"
    "os"
)

func main() {
    reader := bufio.NewReader(os.Stdin)
    writer := bufio.NewWriter(os.Stdout)
    defer writer.Flush()

    var n, m int
    fmt.Fscan(reader, &n, &m)

    dp := make([]int32, n+1)
    S := make([]int32, n+1) // S[i] = dp[1]+...+dp[i]

    dp[1] = 1
    S[1] = 1

    for x := 2; x <= n; x++ {
        // subtraction part: S[x-1]
        val := int64(S[x-1])
        
        // division part: sum dp[floor(x/z)] for z=2..x
        // floor(x/z) for z=2..x, values range from 1 to x/2
        // enumerate distinct values using sqrt decomposition
        z := 2
        for z <= x {
            q := x / z
            // find max z' such that floor(x/z') = q
            // z' = floor(x/q)
            zMax := x / q
            if zMax > x {
                zMax = x
            }
            // count = zMax - z + 1
            count := int64(zMax - z + 1)
            val += count * int64(dp[q])
            z = zMax + 1
        }
        
        dp[x] = int32(val % int64(m))
        S[x] = int32((int64(S[x-1]) + int64(dp[x])) % int64(m))
    }

    fmt.Fprintln(writer, dp[n])
}
```

Let me verify with the example: n=3, m=some prime.
- dp[1]=1, S[1]=1
- x=2: subtraction: S[1]=1. Division: z=2, q=1, zMax=2, count=1, val+=1*dp[1]=1. val=2. dp[2]=2, S[2]=3.
- x=3: subtraction: S[2]=3. Division: z=2, q=1, zMax=3, count=2, val+=2*dp[1]=2. val=5. dp[3]=5. ✓

The answer matches the expected 5.