Calculator

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>

int main(int argc, char **argv){
    if (argc == 2){
        if (strcmp(argv[1], "-s") == 0){
            int sum = 0;
            int num;
            while (scanf("%d", &num) != EOF){ // Ctrl+D
                sum += num;
            }
            printf("Sum = %d\n", sum);
            return EXIT_SUCCESS;
        } else if (strcmp(argv[1], "-p") == 0){
            int product = 1;
            int num;
            while (scanf("%d", &num) != EOF){ // Ctrl+D
                product *= num;
            }
            printf("Product = %d\n", product);
            return EXIT_SUCCESS;
        }
    }
    if (strcmp(argv[1], "-s") == 0){
        int sum = 0;
        for (int i = 2; i < argc; i++){
            sum += atoi(argv[i]);
        }
        printf("Sum = %d\n", sum);
        return EXIT_SUCCESS;
    } else if (strcmp(argv[1], "-p") == 0){
        int product = 1;
        for (int i = 2; i < argc; i++){
            product *= atoi(argv[i]);
        }
        printf("Product = %d\n", product);
        return EXIT_SUCCESS;
    } else if (strcmp(argv[1], "-M") == 0){
        int maxNum = INT_MIN;
        for (int i = 2; i < argc; i++){
            int num = atoi(argv[i]);
            if (num >  maxNum){
                maxNum = num;
            }
        }
        printf("Max number = %d\n", maxNum);
        return EXIT_SUCCESS;
    } else if (strcmp(argv[1], "-m") == 0){
        // min number
        return EXIT_SUCCESS;
    } else {
        fprintf(stderr, "Invalid option!\n");
        return EXIT_FAILURE;
    }
}