Faulty machine problem

machineProblemNSoln.c

#include <stdio.h>
int nextprime(int number);
int isprime(int value);

int main(void)
{
    // let size of each choc. be 50 grm
    long int chocw=50;
    long int expectedw=0;
    long int resultw=0;
    
    long int faultymachine;
    long int faultysize;
    long int totalmachines;    
    long int index=1;
    long int lastnumber=0;
    long int diff=0;
    long int count=1;
    
    
    printf("Enter Total Machines No. \n");
    scanf("%ld",&totalmachines);
    
    printf("Enter weight of each choc \n");
    scanf("%ld",&chocw);
          
    printf("Enter Faulty machine number \n");
    scanf("%ld",&faultymachine);

    printf("Enter Faulty weight (should be less than < %d) \n",chocw);
    scanf("%ld",&faultysize);
        
    // Step 1 calculate weights     
    lastnumber=chocw;
    
    
    for(index=1;index<=totalmachines;index++) {
    
         lastnumber = nextprime(lastnumber);                                        
         expectedw += (lastnumber*chocw);
         
         
         printf("M: %ld - %ld \n",index,lastnumber);
         
         if(index == faultymachine){
                  resultw += (lastnumber*faultysize);
         }else{
                  resultw += (lastnumber*chocw);    
         }
    }       
    
    
    printf("Expected weight = %ld \n",expectedw); 
    printf("Actual   weight = %ld \n",resultw); 
    
    diff = expectedw - resultw;
    
    printf("Difference = %ld",diff);
    
    
    // find prime factors of diff
    
    // Solution
    
    lastnumber = nextprime(chocw);
    
    printf("\n\n-------thinking.......... \n");
    for(count=1;count<=totalmachines;count++)
    {    
    
            printf("M: %ld - %ld \n",count,lastnumber);
    
            for(index=1;index<chocw;index++)
            {
                    if((index * lastnumber) == diff)
                    {
                         printf("\n The Faulty machine is %ld \n",count);
                    }
            }
            lastnumber=nextprime(lastnumber);
    }        
    
    getchar();     
    
    return 1;
}

int nextprime(int number)
{
    while(1)
    {
           ++number;             
           if(isprime(number))              
           {
              return number;                                                                      
           }
    }
}

int isprime(int value){
    int i=2;
    
    for(;i<=value/2;i++){
		if(value%i==0){
			return 0;
		}
    }
    return 1;                               
}