下列程序编译没问题，但是组建有问题，请问错在哪里？
#include <stdio.h>
int mian(void)
{
    int a[15][15],i,j,k,p,n;
    p = 1;
    while(p == 1)
    {
        printf("请输入魔方阵的阶数(该魔方阵的阶数为1到15):\n");
        scanf("%d",&n);
        if((n!=0) && (n%2 != 0) && (n<=15))
            p= 0;
    }
    for (i = 1;i<=n;i++)
    {
        for(j = 1;j<=n;j++)
            a[i][j] = 0;
    }
        j = n/2 + 1;
        a[1][j] = 1;
    for(k = 2;k<=n*n;k++)
    {
        i = i -1;
        j = j + 1;
        if((i<1) && (j > n) )
        {
            i = i + 2;
            j = j - 1;
        }
        else
        {
            if(i<1)
                i = n;
            if(j>n)
                j = 1;
        }
        if(a[i][j] == 0)
            a[i][j] = k;
        else
        {
            i = i + 2;
            j = j - 1;
            a[i][j] = k;
        }

    }
    for(i = 1;i<=n;i++)
    {
        for(j = 1;j<=n;j++)
            printf("%5d",a[i][j]);
        printf("\n");
    }

    return 0;
}

报的错是这样的：
LIBCD.lib(crt0.obj) : error LNK2001: unresolved external symbol _main
Debug/wanjie.exe : fatal error LNK1120: 1 unresolved externals

没办法，才学，看不来错误信息。真诚的说一句：谢谢啊