找不到哪里错了，请求各位帮帮忙~

#include <iostream.h>
int mian()
{
    int a[15]={88,99,1,2,3,4,5,6,7,8,9,10,55,66,1},k=15;
        int sum=a[0]+a[1]+a[2]+a[3];
        int maxsum=sum;
        int maxindex=0;
    for(int i=0;i<k;i++)
    {
        sum=sum-a[i]+a[(i+4)%k];
        if(sum>maxsum)
        {
            maxsum=sum;
            maxindex=(i+1)%15;
        }

    }
    cout<<"the maxsum is:"<<maxsum<<endl;
    cout<<"the maxindex is:"<<maxindex<<endl;
    return 0;

}

错误显示为： fatal error LNK1120: 1 unresolved externals