CS50 PSET 1 hacker bad credit code

#include <stdio.h>
include <cs50.h>
include <stdlib.h>
include <ctype.h>
include <string.h>
include <math.h>
int main(void) {
char name[20]; char dist[3]; long long number = GetLongLong();
sprintf(name, "%lld", number );
int length = strlen(name);
if ( (length != 13) || (length != 15) || (length != 16) ) { printf("INVALID"); return 1; }
int SUM = 0; if ( (length == 13) || (length == 15) ) { for (int a = 1; a < length-1; a+=2) { int prodig = (name[a]-48)* 2; sprintf(dist, "%d", prodig); if (strlen(dist) == 2) { SUM = SUM + (dist[0]-48) + (dist[1]-48); } else { SUM += prodig; } }
   for (int a = 0; a < length; a+=2)
   {
       SUM += (name[a]-48);
   }
}
if (length == 16) { for (int a = 1; a < 17; a+=2) { int prodig = (name[a]-48)* 2; sprintf(dist, "%d", prodig); if (strlen(dist) == 2) { SUM = SUM + (dist[0]-48) + (dist[1]-48); } else { SUM += prodig; } }
   for (int a = 0; a < 15; a+=2)
   {
       SUM += (name[a]-48);
   }
}
if (SUM%10 != 0) { printf("INVALID"); return 1; }
else { if (name[0] == 3) { printf("AMEX"); }
   else if (name[0] == 5)
   {
       printf("MASTERCARD");
   }

   else
   {
       printf("VISA");
   }
}
return 0;
}