Compilare: user.c: In function ‘main’: user.c:33:10: warning: implicit declaration of function ‘malloc’ [-Wimplicit-function-declaration] ar = malloc(sizeof(int)*aSize); ^~~~~~ user.c:33:10: warning: incompatible implicit declaration of built-in function ‘malloc’ user.c:33:10: note: include ‘<stdlib.h>’ or provide a declaration of ‘malloc’ user.c:38:13: warning: assignment makes integer from pointer without a cast [-Wint-conversion] sum += ar+i; ^~ user.c:64:5: warning: implicit declaration of function ‘free’ [-Wimplicit-function-declaration] free(ar); ^~~~ user.c:64:5: warning: incompatible implicit declaration of built-in function ‘free’ user.c:64:5: note: include ‘<stdlib.h>’ or provide a declaration of ‘free’ user.c:29:5: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("transport.in", "rt", stdin); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ user.c:30:5: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("transport.out", "wt", stdout); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ user.c:31:5: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%i%i", &aSize, &nTrips); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ user.c:37:9: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%i", ar+i); ^~~~~~~~~~~~~~~~~