Cplusplus rewriting a code about dooflingy - c++

Question

so I wrote out this c++ program which works, but after submitting it, It was returned back saying it needs to be rewritten since it did not use adjacent_difference, the problem asked is as follows:
The Rinky Dooflingy Company records the number of cases of dooflingies produced each day over a four-week period. Write a program that reads these production levels and stores them in an STL container. The program should then find and display:
a. The lowest, highest, and average daily production level.
b. A sequence that shows how much the production level rose or fell each day.
c. A sequence that shows, for each day, the total number of dooflingies produced up to and including that day.
You must use an Standard Container and you must use standard algorithms to do all the calculations shown in a, b, and c above. Solutions not using a standard container and not using standard algorithms for calculations are not acceptable.
And my feed back was:
A standard algorithm (adjacent_difference) exists to calculate the daily changes but you don't use it.
Does not meet problem spec requiring the use of standard algorithms where available.
Please help, I'm stumped and tried to rewrite it, but haven't succeded
here is my code as follows:
#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
using namespace std;
int main(){
vector<int> product; //set up vector
cout<<"Please enter the number of cases of Dooflingies produced each day:\n"; //prompt user to enter amount produced in a day
for(int i=0; i<5; i++){ //math for vector
int temp;
cin>>temp;
product.push_back(temp);
}
cout<<"-------------------------------";
cout<<"\nHighest Production Level: " <<*std::max_element(product.begin(),product.end())<<"\n"; //display highest production level
cout<<"Lowest Production Level: " <<*std::min_element(product.begin(),product.end())<<"\n"; //display lowest production level
cout<<"Average Production Level: " <<std::accumulate(product.begin(),product.end(),0.0)/product.size()<< "\n"; //display average production level
cout<<"-------------------------------";
cout<<"\nProduction Level Influx:\n"; //display rise in production, used spaces to make it easier to see
for(int i=1; i<28; i++){ //math for vector
cout <<"Day " <<i<<": "<<product[i]-product[i-1]<<"\n";
}
int cumulative_sum[28]; //the cumulative sum of the whole program
std::partial_sum(product.begin(),product.end(),cumulative_sum);
cout<<"-----------------------------\n";
cout<<"Total Production Until:\n"; //total amount of dooflingies produced
for(int i=0;i<28; i++){
cout<<"Day " <<i+1<<": "<<cumulative_sum[i]<<"\n"; //math
}
return 0;
}
Thank you in advance