Grid Traversal

There is a rectangular grid of size m * n . Bob is in location ( x, y ) inside grid. He can move in 4 directions up, down, right and left. He will die if he steps outside of rectangular grid. Find the probability that bob is alive given initial position of bob as ( x, y ) and number of steps he moves as N. (Given that Bob moves only one step at a time).

#include<iostream>
using namespace std;
int main()
{
    void fun(int,int,int,int,float*,float*,int,int);
    int m,n,x,y,N;
    float a=0.0,b=0.0,*p=&a,*q=&b;
    cin>>m>>n>>x>>y>>N;
    fun(m,n,x,y,p,q,0,N);
    cout<<(*q)/((*q)+(*p));
}
void fun(int m,int n,int x,int y,float *p,float *q,int S,int N)
{    
    if(S==N && x>=0 && y>=0 && x<m && y<n)
    {
        (*q)++;
        return;
    }
    else if((S<=N) && (x<0 || y<0 || x>=m || y>=n))
    {
        (*p)++;
        return;
    }
    else
    {
        fun(m,n,x+1,y,p,q,S+1,N);
        fun(m,n,x-1,y,p,q,S+1,N);
        fun(m,n,x,y+1,p,q,S+1,N);
        fun(m,n,x,y-1,p,q,S+1,N);
    }
}