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

//Multiplication tables. 10*x and x*10 are erased because we are treating 1 digit factors multiplications
int mult_tables[9][9]= {{ 1  , 2  , 3  , 4  , 5  , 6  , 7  , 8  , 9  },
                        { 2  , 4  , 6  , 8  , 10 , 12 , 14 , 16 , 18 },
                        { 3  , 6  , 9  , 12 , 15 , 18 , 21 , 24 , 27 },
                        { 4  , 8  , 12 , 16 , 20 , 24 , 28 , 32 , 36 },
                        { 5  , 10 , 15 , 20 , 25 , 30 , 35 , 40 , 45 },
                        { 6  , 12 , 18 , 24 , 30 , 36 , 42 , 48 , 54 },
                        { 7  , 14 , 21 , 28 , 35 , 42 , 49 , 56 , 63 },
                        { 8  , 16 , 24 , 32 , 40 , 48 , 56 , 64 , 72 },
                        { 9  , 18 , 27 , 36 , 45 , 54 , 63 , 72 , 81 }};


/*Function which return value is the last digit of the number given as parameter
  e.g.:
      last_digit(9) => 9
      last_digit(154) => 4
*/
int last_digit(int num){
  int i = 0;
  if(num <10) return num;
  while((num%2 != 0) && (num%5 != 0)){
    i++;
    if((num - i)%2 == 0 && (num - i)%5 == 0){
      return i;
    }
  }
  return i;
}


/*Change the given number in (number -last_digit)/10
  e.g.:
      num_transf(154) => 15
*/
int num_transf(int num, int dig){
  return (num - dig)/10;
}

int el(int n, int e){
  for(int i=0; i<e; i++){
    n *=n;
  }
}



long int mul(int p, int s){
  int eli, elj;//Variables where to store the elevation counters
  long int ret;//Variable to return
  int sum;//Variable where to store the temporary result
  int pd, sd;// Variables where to store the last digits of every factor
  printf("SUCA");
  for(int i=0; p!=0 ; i++){
    pd = last_digit(p);
    if(p >9) p = num_transf(p, pd);//If the number is has more than 1 digit, call the num_transf function
    if(pd != 0){//If the digit is not 0
      for(int j=0; s!=0; j++){
        sd = last_digit(s);
        if(s >9) s = num_transf(s, sd);//If the number is has more than 1 digit, call the num_transf function
        if(sd != 0){//If the digit is not 0
          elj= el(10,j);
          sum += (mult_tables[pd-1][sd-1])*elj;
        //Come devo gestire il riporto?
        }
      }
      eli = el(10,i);
      ret += sum*eli;
    }
    return ret;
  }

}

int main(int argc, char** argv){
  int n, m;
  long int l;
  printf("First factor: ");
  scanf("%d", &n);
  printf("\nSecond factor: ");
  scanf("%d", &m);
  l = mul(n,m);
  printf("\nMultiplication result %d\n", n*m );
  printf("Function result: %ld\n", l);
  return 0;
  }