Simple Menu Program in C 1

#include<stdio.h>
#include<stdlib.h>
#include<math.h>

void lucky();
float ctof();
float sqr();
long int fact();
int a;
void main() {
    int ch;
    while (1) {
        printf("\nMENU");
        printf("\n1.%cC to %cF conversion\n2.Square root of a number");
        printf("\n3.10 Lucky numbers between two numbers");
        printf("\n4.Factorial of given number");
        printf("\n9.Abandon the program",248,248);
        printf("\n\nEnter your choice: ");
        scanf("%d", &ch);
        switch (ch) {
        case 1:
            printf("Temp in %cF is: %.2f\n", 248, ctof());
            break;
        case 2:
            printf("Square root of the number is: %.2f\n", sqr());
            break;
        case 3:
            lucky();
            break;
        case 4:
            printf("Factorial of %d! is: %ld\n", a, fact());
            break;
        case 9:
            exit(1);
        default:
            printf("Invalid choice\n");
        }
    }
}

float ctof() {
    float fah;
    float cel;
    printf("Enter temp in %cC: ", 248);
    scanf("%f", &cel);
    fah = (9 * cel + 160) / 5;
    return (fah);
}

float sqr() {
    float sqr, no;
    printf("Enter the number: ");
    scanf("%f", &no);
    sqr = sqrt(no);
    return (sqr);
}

long int fact() {
    int i;
    long int pro = 1;
    printf("Enter the number: ");
    scanf("%d", &a);
    for (i = 0; (a - i) > 0; i++)
        pro = pro * (a - i);
    return (pro);
}

void lucky() {
    int b, c, i;
    printf("Enter the two numbers: \n");
    scanf("%d%d", &a, &b);
    printf("\n10 Lucky numbers between %d and %d are: \n", a, b);
    for (i = 0; i < 10;) {
        c = rand();
        if ((c > a && c < b) || (c > b && c < a)) {
            printf("%-5d", c);
            i++;
        }
    }
    printf("\n");
}