Postman intern question

Can anyone give optimised solution?

How to handle “Abort called” error on hackerrank?

Why this code gave “Abort called”? It gives correct output for small test cases

int variantsCount(int n, int s0, int k, int b, int m, long a)
{
vector s;
s.push_back(s0);

for(int i=1;i<n;i++) 
    s[i] = ((k%m*s[i-1]%m)%m + b%m)%m + 1 + s[i-1];
    
    
int end=n-1;
long ans=0;
for(int start=0;start<n;start++)
{
          while(end>=0 && (s[start]*s[end])>a)
          end--;
          if(end>=0 &&(s[start]*s[end])<=a)
          ans+=(end+1);
}
return ans;

}