C :

#include<stdio.h>
#define N 200907
int main()
{
    long long a,b,c,d,tmp;
    int i,j,k,n,m;
    while(scanf("%d",&n)!=EOF)
    {
        for(m=0;m<n;m++)
        {
            scanf("%lld%lld%lld%d",&a,&b,&c,&k);
            if(b-a==c-b)
            {
                tmp=(b-a)%N;
                d=((k-3)%N*tmp+c%N)%N;
            }
            else if(b/a==c/b)
            {
                tmp=(c/b)%N;
                d=1;
                k--;
                while(k!=0)
                {
                    j=k%2;
                    if(j==1)
                    {
                        d*=tmp;
                        d%=N;
                    }
                    tmp=(tmp*tmp)%N;
                    k/=2;
                }
                d=d*(a%N)%N;
            }
            printf("%lld\n",d);
        }
    }
    return 0;
}

C++ :

#include<stdio.h>
#define MOD 200907

long long modular_exponent(long long a,long long b,int n){ //a^b mod n
    long long ret=1;
    for (;b;b>>=1,a=(long long)(((long long)a)*a%n))
        if (b&1)
            ret=(long long)(((long long)ret)*a%n);
    return ret;
}


int main()
{
    double a,b,c;
    int T;
    int k;
    scanf("%d",&T);
    while(T--)
    {
        scanf("%lf%lf%lf%d",&a,&b,&c,&k);
        if(a+c==2*b)
        {
            long long a1=(long long )a;
            long long d=(long long )(b-a);
            int ans=(a1%MOD+((k-1)%MOD)*(d%MOD))%MOD;
            printf("%d\n",ans);
        }
        else
        {
            long long a1=(long long )a;
            long long t1=(long long )(a1%MOD);
            double q1=(b/a);
            long long q2=(long long)q1;
            long long q=(long long)(q2%MOD);
            long long tmp=modular_exponent(q,k-1,MOD);
            int ans=(t1*tmp)%MOD;
            
            
            printf("%d\n",ans);
        }
    }
    return 0;
}