#include <stdio.h>
#include <stdlib.h>


const int M=-1 ;

int main() {

    int x, r ;  
    int s=0 ; 


    printf("entrez une valeur entiere \n") ;

    r = scanf ("%d", &x) ;
    // we simply check that the return value of scanf is 1
    // (the expected number of correctly read input value)
    if (r!=1) exit(1) ; // exit if scanf failed to read an integer value

    while (x != M) {
        
	s = s + x ;  
        printf("entrez une valeur entiere \n") ;
	r = scanf ("%d", &x) ;
    	// we simply check that the return value of scanf is 1
    	// (the expected number of correctly read input value)
    	if (r!=1) exit(1) ; // exit if scanf failed to read an integer value

    } ; 

    printf("le resultat est %d \n", s) ;
   return 0 ;

}