01problem.c

#include <stdio.h>

int main()
{
    int marks1, marks2, marks3;
    float average;

    // marks input
    printf("Enter marks1:");
    scanf("%d", &marks1);

    printf("Enter marks2:\n");
    scanf("%d", &marks2);

    printf("Enter marks3:\n");
    scanf("%d", &marks3);

    // average calculation
    average = (marks1 + marks2 + marks3) / 3.0;

    printf("The average is %.2f\n", (marks1 + marks2 + marks3) / 3);

    // applying average and printing grades
    if (average > 33 && average < 55)
    {
        printf("Congratulations ! you are passed\n");
        printf("Your grade is D");
    }
    else if (average > 55 && average < 60)
    {
        printf("Congratulations ! you are passed\n");
        printf("Your grade is C");
    }
    else if (average > 55 && average < 60)
    {
        printf("Congratulations ! you are passed\n");
        printf("Your grade is B");
    }
    else if (average > 90 && average < 100)
    {
        printf("Congratulations ! you are passed\n");
        printf("Your grade is A");
    }
    else if (average < 33)
    {
        printf("Unfortunately! you are failed bro\n");
        printf("Your grade is E");
    }

    return 0;
}