#include
int main()
{
int n,i;
while(scanf("%d",&n)==1)
for(i=n>999?n+1:1000;i<10000;++i)
if((i%100)*(i%100)+(i/100)*(i/100)==i)
printf("%d\n",i);
break;
}
if(i>9999)
printf("-1\n");
return 0;
