Help me in solving LCPPAS60 problem

My issue

Write a program to print the grades of a student based on the marks they have obtained provided as input. The student is graded A if marks are greater than 90, B if marks are greater than 70, C if greater than or equal to 40, else F.

My code

 #include <iostream>
using namespace std;

int main() {
	// your code goes here

}

Learning course: Learn Programming and Problem Solving using C++
Problem Link: https://www.codechef.com/learn/course/sit-cpp-fall/PROGC04/problems/LCPPAS60