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problem_37.c
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problem_37.c
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#include <stdio.h>
#include <math.h>
static int is_prime( unsigned long p )
{
if( p < 2 ) {
return 0;
}
if( p == 2 ) return 1;
if( p % 2 == 0 ) return 0;
unsigned long i;
for( i = 3; i <= sqrt( p ); i+=2 ) {
if( p % i == 0 ) {
return 0;
}
}
return 1;
}
int main( )
{
int n = 11;
int prime_num = 0, prime_sum = 0;
while( n++ ) {
if( !is_prime( n ) ) {
continue;
}
int fail = 0, t = n;
while( t /= 10 ) {
if( !is_prime( t ) ) {
fail = 1;
break;
}
}
if( fail ) continue;
fail = 0, t = n;
while( 1 ) {
int r = t, n = 1;
while( r / 10 ) { r /= 10; n *= 10; }
t -= r * n;
if( !t ) break;
if( !is_prime( t ) ) {
fail = 1;
break;
}
}
if( fail ) continue;
prime_num++;
prime_sum += n;
if( prime_num == 11 ) {
break;
}
}
printf( "Answer: %d\n", prime_sum );
}