Compilare: main.cpp: In function 'int ok(int)': main.cpp:37:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for ( i = val ; i < s.size () ; ++ i ) ~~^~~~~~~~~~~ main.cpp:47:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for ( i = 1 ; i < s.size () - val + 1 ; ++ i ) ~~^~~~~~~~~~~~~~~~~~~~~ main.cpp:20:28: warning: unused variable 'h2' [-Wunused-variable] long long i , h1 = 0 , h2 = 0 , p1 , p2 , l = 0 ; ^~ main.cpp:20:42: warning: unused variable 'p2' [-Wunused-variable] long long i , h1 = 0 , h2 = 0 , p1 , p2 , l = 0 ; ^~