Compilare: user.c: In function ‘main’: user.c:9: warning: conversion lacks type at end of format user.c:9: warning: too many arguments for format user.c:7: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:8: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:9: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result