#include<cstdio>
int f[1001][1001],ans;
inline int readint()
{
int i=0;
char ch;
for(ch=getchar();ch<'0'||ch>'9';ch=getchar());
for(;ch>='0' && ch<='9';ch=getchar())
i=(i<<3)+(i<<1)+ch-'0';
return i;
}
int max(int a,int b)
{
return a>b?a:b;
}
int main()
{
int n;
n=readint();
for(int i=1;i<=n;++i)
for(int j=1;j<=i;++j)
f[i][j]=readint();
for(int i=1;i<=n;++i)
for(int j=1;j<=i;++j)
f[i][j]+=max(f[i-1][j-1],f[i-1][j]);
for(int i=1;i<=n;++i) ans=max(ans,f[n][i]);
int num=0;
char c[12];
do
{
c[++num]=(ans%10)+48;
ans/=10;
}while(ans);
while(num) putchar(c[num--]);
return 0;
}

The number 151 is a prime palindrome because it is both a prime number and a palindrome (it is the same number when read forward as backward). Write a program that finds all prime palindromes in the range of two supplied numbers a and b (5 <= a < b <= 100,000,000); both a and b are considered to be within the range .

PROGRAM NAME: pprime

INPUT FORMAT

SAMPLE INPUT (file pprime.in)

5 500

OUTPUT FORMAT

SAMPLE OUTPUT (file pprime.out)

5
7
11
101
131
151
181
191
313
353
373
383

#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <stdlib.h>
FILE *fout;
long a, b;
int
isprime(long n)
{
long i;
if(n == 2)
return 1;
if(n%2 == 0)
return 0;
for(i=3; i*i <= n; i+=2)
if(n%i == 0)
return 0;
return 1;
}
void
gen(int i, int isodd)
{
char buf[30];
char *p, *q;
long n;
sprintf(buf, "%d", i);
p = buf+strlen(buf);
q = p - isodd;
while(q > buf)
*p++ = *--q;
*p = '';
n = atol(buf);
if(a <= n && n <= b && isprime(n))
fprintf(fout, "%ldn", n);
}
void
genoddeven(int lo, int hi)
{
int i;
for(i=lo; i<=hi; i++)
gen(i, 1);
for(i=lo; i<=hi; i++)
gen(i, 0);
}
void
generate(void)
{
genoddeven(1, 9);
genoddeven(10, 99);
genoddeven(100, 999);
genoddeven(1000, 9999);
}
void
main(void)
{
FILE *fin;
fin = fopen("pprime.in", "r");
fout = fopen("pprime.out", "w");
assert(fin != NULL && fout != NULL);
fscanf(fin, "%ld %ld", &a, &b);
generate();
exit (0);
}

Butchering Farmer John's cows always yields the best prime rib. You can tell prime ribs by looking at the digits lovingly stamped across them, one by one, by FJ and the USDA. Farmer John ensures that a purchaser of his prime ribs gets really prime ribs because when sliced from the right, the numbers on the ribs continue to stay prime right down to the last rib, e.g.:

7
3
3
1

The set of ribs denoted by 7331 is prime; the three ribs 733 are prime; the two ribs 73 are prime, and, of course, the last rib, 7, is prime. The number 7331 is called a superprime of length 4.

Write a program that accepts a number N 1 <=N<=8 of ribs and prints all the superprimes of that length.

The number 1 (by itself) is not a prime number.

PROGRAM NAME: sprime

INPUT FORMAT

SAMPLE INPUT (file sprime.in)

4

OUTPUT FORMAT

SAMPLE OUTPUT (file sprime.out)

2333
2339
2393
2399
2939
3119
3137
3733
3739
3793
3797
5939
7193
7331
7333
7393

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
FILE *fout;
int
isprime(int n)
{
int i;
if(n == 2)
return 1;
if(n%2 == 0)
return 0;
for(i=3; i*i <= n; i+=2)
if(n%i == 0)
return 0;
return 1;
}
/* print all sprimes possible by adding ndigit digits to the number n */
void
sprime(int n, int ndigit)
{
if(ndigit == 0) {
fprintf(fout, "%dn", n);
return;
}
n *= 10;
if(isprime(n+1))
sprime(n+1, ndigit-1);
if(isprime(n+3))
sprime(n+3, ndigit-1);
if(isprime(n+7))
sprime(n+7, ndigit-1);
if(isprime(n+9))
sprime(n+9, ndigit-1);
}
void main(void)
{
int n;
FILE *fin;
fin = fopen("sprime.in", "r");
assert(fin != NULL);
fout = fopen("sprime.out", "w");
assert(fout != NULL);
fscanf(fin, "%d", &n);
sprime(2, n-1);
sprime(3, n-1);
sprime(5, n-1);
sprime(7, n-1);
exit (0);
}