C program to sum two integers

input:
 stdin 0 -> progname :: string
 stdin 1 -> x :: string
 stdin 2 -> y :: string

output:
 stdout -> x + y :: string

programming language:
 C99

considerations:
 security paranoid programming

#include <stdio.h>
#include <gmp.h>

int main(int argc, char *argv[argc])
{ mpz_t s, n; mpz_inits(s, n, NULL);
  for(int i = 1; i < argc; mpz_add(s, s, n))
    mpz_set_str(n, argv[i++], 10);
  mpz_out_str(stdout, 10, s);
  mpz_clears(s, n, NULL); }