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

int main(){
    long long double x=1;

    long long double epsbig=x, epsmall=0;
    for(;;){
        long long double epsilon=(epsbig+epsmall)/2;
        long long double y=x+epsilon;
        if(x==y){
            printf("x+%.17Lg rounded back to x.\n",epsilon);
            if(epsmall==epsilon) break;
            epsmall=epsilon;
        } else {
            printf("x+%.17Lg was something else.\n",epsilon);
            if(epsbig==epsilon) break;
            epsbig=epsilon;
        }
    }
    printf("The size of x is %ld\n",sizeof(x));
    printf("the largest epsilon such that x+epsilon rounds\n"
        "back to x is %.17Lg\n",epsmall);
    return 0;
}