polynomial multiplication using linked list in c not working - c

Question

#include<stdio.h>
#include<stdlib.h>
struct node{
float coeff;
int exp;
struct node *next;
};
struct node*inserts(struct node *start,float co,int ex){
struct node*newnode;
struct node*ptr;
newnode=(struct node*)malloc(sizeof(struct node));
newnode->exp=ex;
newnode->coeff=co;
if(start==NULL||start->exp<ex){
newnode->next=start;
start=newnode;
}
else{
ptr=start;
while(ptr->next!=NULL&&ptr->exp>ex){
ptr=ptr->next;
}
newnode->next=ptr->next;
ptr->next=newnode;
}
return start;
}
struct node*create(struct node *start){
int ex,n;
float co;
printf("enter the number of terms\n");
scanf("%d",&n);
for(int i=0;i<n;i++){
printf("enter your coefficient\n");
scanf("%f",&co);
printf("enter your exponent\n");
scanf("%d",&ex);
start=inserts(start,co,ex);
}
return start;
}
struct node* polymulti(struct node *start1,struct node *start2){
struct node*p2;
struct node *p1;
struct node *start3;
p1=start1;
p2=start2;
while(p1!=NULL){
while(p2!=NULL){
start3=inserts(start3,p2->coeff*p1->coeff,p2->exp*p1->exp);
p2=p2->next;
}
p1=p1->next;
}
return start3;
}
void display(struct node*st){
struct node *temp;
temp=st;
while(temp->next!=NULL){
printf("%.1fx^%d",temp->coeff,temp->exp);
printf("+");
temp=temp->next;
}
printf("%.1fx^%d",temp->coeff,temp->exp);
}
int main(){
struct node*start1;
struct node*start2;
struct node*start3;
start1=create(start1);
start2=create(start2);
start3=polymulti(start1,start2);
display(start3);
return 0;
}
i am working on a program that accepts two polynomials and then displays the product of the two polynomials .i have created three linked list ,two of which are used to input the two polynoimals and third is used to display the product. However when i was inserting values into the 2nd linked list ,the program abruptly ended without giving any errors or warning. can anybody tell whats the problem here?