Here is my code. Please help to find mistake.
#include <stdio.h>
void main()
{
int x,n,m,y,p,i,s,u;
vv:
scanf("%d",&n);
scanf("%d",&m);
scanf("%d",&y);
if (n<=0 || n>=999 || m<=1 || m>=999 || y<=0 || y>=99) goto vv;
u=-1;
s=0;
x=0;
while (x<=(m-1))
{
 p=1;
 for (i=1; i<=n; i++)
 {
  p=p*x;
 }
 if ((p % m) == y)
 {
 printf("%d ",x);
 s++;
 }
 x++;
}
 if (s==0)
 printf("%d\t",u);
}