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From: kym@bingvaxu.cc.binghamton.edu (R. Kym Horsell)
Subject: Re: Subtle Math Questions
Message-ID: <1991Apr30.131955.17083@bingvaxu.cc.binghamton.edu>
Organization: State University of New York at Binghamton
References: <1991Apr30.002142.21112@jarvis.csri.toronto.edu> <1991Apr30.072900.7073@bingvaxu.cc.binghamton.edu> <1991Apr30.080102.9990@bingvaxu.cc.binghamton.edu>
Date: Tue, 30 Apr 1991 13:19:55 GMT

In article <1991Apr30.002142.21112@jarvis.csri.toronto.edu> blaak@csri.toronto.edu (Raymond Blaak) writes:
>ghot@ms.uky.edu (Allan Adler) writes:
>>(6) What are the last 4 digits of 5 to the 7777th power ?
>
>How about the FIRST 4 digits?
>
>Cheers,
>Ray

As I've had several requests for the secret of my posted solution:

/* calculate ms 4 digits of 5^7777 */

ipow(ix,iy) {
	double u=1;
	double x=ix;
	while(x>1) x/=10;
	while (iy) {
		if(iy&1) {
			u*=x;
			while(10*u<1) u*=10;
			}
		x*=x;
		while(10*x<1) x*=10;
		iy>>=1;
		}
	return u*10000;
	}

main() {
	printf("%d\n",ipow(5,7777));
	}

-kym