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

double atof();
double log();

main(argc, argv)
int argc;
char *argv[];
{
char tmp[200];
double prin = 0;
double monpay = 0;
double interest = 0;
double length = 0;

if ((argc == 2) && ((argv[1][0] == 'p') || (argv[1][0] == 'P')))
	{
	 fprintf(stdout,"Enter principal amount <$>.............. ");
	 fgets(tmp,100,stdin);
	 prin = atof(tmp);
	 fprintf(stdout,"Enter monthly payment <$>............... ");
	 fgets(tmp,100,stdin);
	 monpay = atof(tmp);
	 fprintf(stdout,"Enter annual interest rate.............. ");
	 fgets(tmp,100,stdin);
	 interest = atof(tmp) / 100;
	 fprintf(stdout,"\n");
	}
else if ((argc == 2) && ((argv[1][0] == 'v') || (argv[1][0] == 'V')))
	{
	 fprintf(stdout,"loanlen: Version 1.00 \n");
	 fprintf(stdout,"         Copyright 1987 by Michael Brochstein\n");
	 fprintf(stdout,"         All rights reserved.\n");
	}
else if (argc != 4) 
	{
	 fprintf(stderr,"Usage: loanlen p \n");
	 fprintf(stderr,"       loanlen v \n");
	 fprintf(stderr,"       loanlen <principal> <monthly payment>");
	 fprintf(stderr," <annual interest rate>\n");
	}
else if (argc == 4)
	{
	 prin = atof(argv[1]);
	 monpay = atof(argv[2]);
	 interest = atof(argv[3]) / 100;
	}

if ((argc == 4) 
	|| ((argc == 2) && ((argv[1][0] == 'p') || (argv[1][0] == 'P'))))
	{
	 length = log(1 - ((interest/12 * prin) / monpay));
	 length = -1 * length / log(1 + interest/12);
	 fprintf(stdout,"Number of monthly payments needed...... %.2f\n",
		length);
	}
}