foo.cc: In function 'int read()':
foo.cc:3:46: warning: 'c' is used uninitialized in this function [-Wuninitialized]
 int ret=0;int read(){char c;ret=0;while(c>'9'||c<'0')c=getchar();while(c<='9'&&c>='0')ret=ret*10+c-'0',c=getchar();return ret;}
                                         ~~~~~^~~~~~~

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