Compilare: main.cpp: In function 'int main()': main.cpp:17:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (size_t a1 = 1; a1 <= 2 * b; a1++) ~~~^~~~~~~~ main.cpp:19:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (size_t c1 = 1; c1 <= 2 * b; c1++) ~~~^~~~~~~~ main.cpp:13:6: warning: unused variable 'a' [-Wunused-variable] int a, b, c; ^ main.cpp:13:12: warning: unused variable 'c' [-Wunused-variable] int a, b, c; ^