Write a C program that asks the user to enter an integer number greater than 9, then calculates the sum of the first and the last digits of the number.

Running example:
Input a number greater than 9: -12
Input a number greater than 9: 925
Sum of the first and the last digits: 14

#include <stdio.h>
int main()
{
    int nb, sum;
    
    do{
        printf("Input a positive number: ");
        scanf("%d",&nb);
    }while(nb<10);
    
    sum = nb%10;
    while(nb>=10)
        nb/=10;
    sum +=nb;
    printf("Sum of the first and the last digits: %d", sum);
    return 0;
}