write a code to calculate average of 5 marks

#include <iostream>
using namespace std;

int main() {
    int s1,s2,s3,s4,s5,avg;
    
    cout << "Enter the s1 marks: " << endl;
    cin >> s1;
    
    cout << "enter the s2 marks:" << endl;
    cin >> s2;
    
    cout << "enter the s3 marks:" << endl;
    cin >> s3;
    
    cout << "enter the s4 marks:" << endl;
    cin >> s4;
    
    cout << "enter the s5 marks:" << endl;
    cin >> s5;
    avg=(s1+s2+s3+s4+s5)/5;
    
    if (avg >=90 and avg <=100) {
        cout << "Your grade is O." << endl;
    } 
    else if(avg >=85 and avg<=90){
        cout << "your grade is A+." << endl;
    }
    else if(avg >=70 and avg<=85){
        cout << "Your grade is B+" << endl;
    }
    else if(avg >=60 and avg<=70){
        cout << "your grade is B." << endl;
    }
    else if (avg>=55 and avg<=60){
        cout<< "your grade is C" << endl;
    }
else{
    cout<< "your grade is F" << endl;
  }
    return 0;
}