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#include <stdlib.h>
#include <stdio.h>
#include <ctype.h>
int c;
void match( char t )
{
if( c == t ) {
c = getc( stdin );
} else {
fprintf( stderr, "\nERR: expecting '%c', but got '%c'\n", t, c );
exit( 1 );
}
}
void term( void )
{
if( isdigit( c ) ) {
int t = c;
match( c );
putchar( t );
} else {
fprintf( stderr, "\nERR: expecting digit, but got '%c'\n", c );
exit( 1 );
}
}
void rest( void )
{
if( c == '+' ) {
match( '+' ); term( ); putchar( '+' ); rest( );
} else if( c == '-' ) {
match( '-' ); term( ); putchar( '-' ); rest( );
}
}
void expr( void )
{
term( ); rest( );
}
int main( void )
{
c = getc( stdin );
expr( );
if( ( c = getc( stdin ) ) != EOF ) {
fprintf( stderr, "\nERR: superfluos input found\n" );
exit( 1 );
}
puts( "" );
exit( 0 );
}
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