an.cpp: In function `int prim(int)': an.cpp:22: call of overloaded `sqrt(int&)' is ambiguous /usr/include/bits/mathinline.h:441: candidates are: double sqrt(double) /usr/include/c++/3.2.2/cmath:465: long double std::sqrt(long double) /usr/include/c++/3.2.2/cmath:461: float std::sqrt(float)