Go4Expert - input file problem

I write a code for a problem. My roblem is:
Enter n x m integers from text file
Arrange above integers on the way from from outside to inside in a certain order of the matrix nx m.
Export results to a text file.
I don't know how to make "input.txt" to make the program run perfectly. If u can, please send me ur file "input.txt"
Here is my code:

Code:

#include <stdio.h>



#define MAXN 110



int a[MAXN][MAXN], m, n;



void input(){

    scanf("%d %d", &n, &m);

}



void initial(){

    int i;

    for (i = 0; i<=n+1; ++i){

        a[i][0]=-1;

        a[i][m+1]=-1;

    }

    for (i = 0; i<=m+1; ++i){

        a[0][i]=-1;

        a[n+1][i]=-1;

    }

}



void solve(){

    int dx[] = {-1, 0 , 1, 0};

    int dy[] = {0, 1, 0, -1};

    int tx = 1, ty = 1, dir = 0, i;

    a[1][1] = 1;

    for (i = 2; i<=n*m; ++i){

        while (a[tx+dx[dir]][ty+dy[dir]]){

            dir = (dir+1)%4;

        }

        tx = tx + dx[dir];

        ty = ty + dy[dir];

        a[tx][ty] = i;

    }

}



void output(){

    int i, j;

    for (i = 1; i<=n; ++i){

        for (j = 1; j<=m; ++j){

            printf("%4d ", a[i][j]);

        }

        printf("\n");

    }

}



int main(){

    freopen("D:\input.txt", "r", stdin);

    freopen("D:\output.txt", "w", stdout);

    input();

    initial();

    solve();

    

    output();

    return 0;

}