C algorithm declare first num character in a Int

FirstInt.c

#include <stdio.h>
void Process(int a){
    int n;
    for (int i = 10; i <=a;){
         a = a/10;
    }
    printf("Chu so dau tien cua so a la : %d ", a);
}
void main() {
    int a;
    printf("Nhap vao so a : ");
    scanf("%d", &a);
    Process(a);

}