Menu based C-Program 1

/*A menu program to check if the given number is odd or even, to find the sum of N natural numbers and to find the sum of squares of two numbers*/
#include<stdio.h>
#include<stdlib.h>

void main() {
    int ch;
    char y;
    int n, a, sum = 0;
    while (1) {
        printf("\nMENU");
        printf("\n1.To check if the given no is odd or even");
        printf("\n2.To find the sum of N numbers");
        printf("\n3.To find the sum of squares of two numbers");
        printf("\n4.Exit from Program");
        printf("\nEnter the choice: ");
        scanf("%d", &ch);
        switch (ch) {
        case 1:
            printf("\nEnter the no. ");
            scanf("%d", &n);
            if ((n % 2) == 0)
                printf("\nIt is even");
            else
                printf("\nIt is odd");
            break;
        case 2:
            printf("\nEnter the value of N: ");
            scanf("%d", &n);
            for (a = 1; a <= n; a++)
                sum = sum + a;
            printf("\nSum= %d", sum);
            break;
        case 3:
            printf("\nEnter the two numbers: ");
            scanf("%d,%d", &a, &n);
            sum = a * a + n * n;
            printf("\nSum of squares is: %d", sum);
            break;
        case 4:
            exit(1);
        default:
            printf("\nInvalid choice");
        }
    }
}