#include <dlfcn.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <stdint.h>
#include <inttypes.h>
#include <sys/wait.h>

void compile_func_file(char * function) {
    const char scriptName[] = "func.c";
    int f = open(scriptName, O_WRONLY | O_TRUNC | O_CREAT, 0666);

    char begin[] =
        "#include <math.h>\n"
        "double f(double x) {\n"
        "    return ";

    write(f, begin, strlen(begin));
    write(f, function, strlen(function));

    char end[] =
        ";\n"
        "}";
    write(f, end, sizeof(end) - 1);
    close(f);

    if (fork() == 0) {
        execlp("gcc", "gcc", scriptName, "-lm", "-c", "-o", "func.o", "-fPIC", NULL);
        _exit(1);
    }
    wait(NULL);

    if (fork() == 0) {
        execlp("gcc", "gcc", scriptName, "-lm", "-shared", "-o", "func.so", NULL);
        _exit(1);
    }
    wait(NULL);
}

int main(int argc, char *argv[]) {
    compile_func_file(argv[4]);
    void *handle = dlopen("./func.so", RTLD_LAZY);
    void *sym = dlsym(handle, "f");

    double left = strtod(argv[1], NULL), right = strtod(argv[2], NULL);
    long long n = strtoll(argv[3], NULL, 10);
    double dx = (right - left) / n;

    double sum = 0;
    for (long long i = 0; i < n; ++i) {
        double xi = left + i * dx;
        sum += ((double (*)(double)) sym)(xi) * dx;
    }
    dlclose(handle);
    printf("%.10g\n", sum);
}