Write a program in C to Check if a number is Mersenne number or not a Mersenne number

# include <stdio.h>
# include <stdlib.h>
# include <math.h>


int main()
{
    int n,p,ans,i,n1;
	double result;
	printf("\n\n Check whether a given number is Mersenne number or not:\n");
	printf("------------------------------------------------------------\n");
	printf(" Input a number: ");
    scanf("%d",&n);
    n1=n+1;
        p = 0;
        ans = 0;
        for(i=0;;i++)
        {
            p=(int)pow(2,i);
            if(p>n1)
            {
                break;
            }
            else if(p==n1)
            {
               printf(" %d is a Mersenne number.\n",n);
               ans=1;
            }
        }
  if(ans==0)
  {
   printf(" %d is not a Mersenne number.\n",n);
  }	
}