Compilare: main.cpp: In function 'long long int fast_pow(long long int, long long int)': main.cpp:8:20: warning: unused variable 'p' [-Wunused-variable] long long r = 1, p = a; ^ main.cpp: In function 'int main()': main.cpp:24:26: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%lld", &n); ^ main.cpp:13:11: warning: 'f3' may be used uninitialized in this function [-Wmaybe-uninitialized] a = a * a % M; ~~^~~ main.cpp:22:31: note: 'f3' was declared here long long n, i, f1 = 1, f2, f3; ^~ main.cpp:13:11: warning: 'f2' may be used uninitialized in this function [-Wmaybe-uninitialized] a = a * a % M; ~~^~~ main.cpp:22:27: note: 'f2' was declared here long long n, i, f1 = 1, f2, f3; ^~