message: Fixed += function of mersenne int element
diff: @@ -149,7 +149,14 @@ public:
  return answer;
  }
  - ZpMersenneIntElement& operator+=(const ZpMersenneIntElement& f2){ elem = (f2.elem + elem) %p; return *this;};
  + ZpMersenneIntElement& operator+=(const ZpMersenneIntElement& f2){
  + elem = (f2.elem + elem);
  +
  + if(elem>=p)
  + elem-=p;
  +
  + return *this;
  + };
  ZpMersenneIntElement& operator*=(const ZpMersenneIntElement& f2)
  {
  long multLong = (long)elem * (long) f2.elem;
  