prisme.cpp: In function `int valid(int, int)': prisme.cpp:15: warning: `int x' might be used uninitialized in this function prisme.cpp:15: warning: `int y' might be used uninitialized in this function prisme.cpp: In function `void Back(int)': prisme.cpp:36: warning: `int v1' might be used uninitialized in this function prisme.cpp:36: warning: `int v2' might be used uninitialized in this function