Compilare: main.cpp: In function 'void build(int, int)': main.cpp:25:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int w = 1; w < v[k].size() ; ++w){ ~~^~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:47:9: warning: unused variable 'nr1' [-Wunused-variable] int nr1 = 0, nr0 = 0; ^~~ main.cpp:47:18: warning: unused variable 'nr0' [-Wunused-variable] int nr1 = 0, nr0 = 0; ^~~ main.cpp:40:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("plus.in", "r", stdin); ^ main.cpp:41:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("plus.out", "w", stdout); ^ main.cpp:43:20: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &S); ^ main.cpp:45:39: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &nr[i], &val[i]); ^