// Online C compiler to run C program online
#include <stdio.h>
#include <math.h>
#define bool int
#define true 1
#define false 0
void skip_ws(const char** s) {
while (**s > 0 && **s <= ' ') (*s)++;
}
double get_sign(const char** s) {
return **s == '-'
? (*s)++, -1
: **s == '+' ? (*s)++, 1 : 1;
}
double parse_int(const char** s) {
double r = 0;
for (; **s >= '0' && **s <= '9'; (*s)++)
r = r * 10 + **s - '0';
return r;
}
bool try_str2real(const char* text, double* const r) {
skip_ws(&text);
double m_sign = get_sign(&text);
const char* s = text;
*r = parse_int(&s);
if (*s == '.') {
s++;
for (double p = 0.1; *s >= '0' && *s <= '9'; s++, p *= 0.1)
*r += p * (*s - '0');
}
*r *= m_sign;
if (text == s || (text == s - 1 && *text == '.')) return false;
if (*s == 'e' || *s == 'E') {
s++;
double p_sign = get_sign(&s);
const char* sp = s;
*r *= pow(10, p_sign * parse_int(&s));
if (sp == s) return false;
}
skip_ws(&s);
return !*s;
}
int main() {
double d;
if (try_str2real("+3.14e0", &d)) printf("%lf", d);
else printf("NAN");
return 0;
}
