#include <stdio.h>

struct vertex
{
  float x;
  float y;
};

int main (void)
{
  int numberVertices;
  int i, j = 0;

  printf("How many vertices do you have?\n");
  scanf("%i", &numberVertices);

  struct vertex vertices [numberVertices];

  do {
    printf("enter x: ");
    scanf("%f", &vertices[i].x);
    printf("enter y: ");
    scanf("%f", &vertices[i].y);
    i++;
  } while (i < numberVertices);

  printf ("Here are your vertices:\n");

  for ( j = 0; j != i; j++)
    printf("%f, %f\n", vertices[j].x, vertices[j].y);

  return 0;
}