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#include <stdlib.h>
#include <ctype.h>
long atol(const char *s)
{
long n=0;
int neg=0;
while (isspace(*s)) s++;
switch (*s) {
case '-': neg=1;
case '+': s++;
}
/* Compute n as a negative number to avoid overflow on LONG_MIN */
while (isdigit(*s))
n = 10*n - (*s++ - '0');
return neg ? n : -n;
}
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