Compilare: user.cpp: In function ‘long long unsigned int prod(long long unsigned int, long long unsigned int)’: user.cpp:14:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=a+1; j<=b; j++) ^ user.cpp: In function ‘int main()’: user.cpp:31:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=1;i<=n-1;i++) ^ user.cpp:35:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=1;i<=r;i++) ^ user.cpp:42:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=1;i<=n-1-r;i++) ^ user.cpp:62:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=lims;i<=n-1;i++) ^