void extendgcd(long long a,long long b,long long &d,long long &x,long long &y){    if(b==0){d=a;x=1;y=0;return;}    extendgcd(b,a%b,d,y,x);    y -= x*(a/b);}//求解A+C*x=B(mod D)，返回最小非负整数xlong long ModX(long long A,long long B,long long C,long long D){    if(A==B)    {        return 0;    }    if(C==0)    {        return -1;    }    long long x,y,tmpd;    extendgcd(C,D,tmpd,x,y);    if( (B-A)%tmpd != 0 )    {        return -1;    }    else    {        x *= (B-A)/tmpd;        long long mod = D/tmpd;        x = (x%mod+mod)%mod;        return x;    }}