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

main()
{
    double eps ;
    double a, b ;
    double c ;

    printf("input a \n");
    scanf("%lf", &a );

    printf("input b \n");
    scanf("%lf", &b );

    if( b<=a || cos(a)*cos(b)>0.0 ){
	fprintf( stderr, "illegal interval %g %g\n", a, b );
        exit(1);
    }

    printf("input epsilon \n");
    scanf("%lf", &eps );

    if( eps<=0 ){
	fprintf( stderr, "illegal accuracy %g\n", eps );
        exit(1);
    }

    while( (A)________  )
    {
        c = (B)________ ;
        if( cos(a) * cos(c) <0 ) {
            b = c;
        } else {
           (C)________ = c;
        }
    }

   c=( a + b )/2.0 ;
   printf( "%g (f(c)=%g)\n", c , cos( c ) );
}