I get too many WA with this problem (1118). In test number 3
I just use a simple algorithm, if lower number is 1 then print 1
else go in a loop from j to l, I mean from the max number until the min. number and start to calculate the nontrivial number of every number until I find a prime, if I find a prime then I print the least nontrivial number until this number (including the first prime that I found)
here is my code:

#include <stdio.h>
#include <math.h>
double s,res=2147483647;
int r=1,rs;

calc(int n,int p){
    int i,k=1;
    p++;
    for(i=0;i<p;i++) k*=n;
    k=(k-1)/(n-1);
    r*=k;
}

fact(int n){
    int p=0,i=3,l=sqrt(n)+1;
    double t=n;
    while(n%2==0){
         n/=2;
         p++;
    }
    if(p>0){
        calc(2,p);
        p=0;
    }
  while(i<l){
     while(n%i==0){
         n/=i;
         p++;
     }
     if(p>0){
         calc(i,p);
         p=0;
     }
     i+=2;
  }
    if(n>1) calc(n,1);
    r-=t;
    s=r/t;
    if(s<res){
        rs=t;
        res=s;
    }
  r=1;
}

is_prime(n){
    int i=3,l=sqrt(n)+1;
    if(n%2==0) return 0;
    for(i=3;i<l;i+=2)
     if(n%i==0) return 0;
     return 1;
}

int main(){
    int l,i,j;
    scanf("%d %d",&l,&j);
    if(l==1) printf("1\n");
    else{
     for(i=j;i>=l;i--) {
       fact(i);
       if(is_prime(i)) break;
   }
  printf("%d",rs,res);
  }
  return 0;
}

if someone can help me I would appreciate very much!!
thanks

I search the greatest prime in the interval. If there are not any primes then we go brute force