#include <stdio.h>
int main() {

    char S[127];
    int i = 0;
    printf("input string:");
    gets(S);

    for(i; S[i] == ' ';++i)
    S[i] = S[i+1]
    for(i = 0; S[i] != '\0';++i)
    if((S[i] == ' ')&&(S[i+1]== ' ')||(S[i+1]== '\0'))
    S[i] = S[i+1];
    puts(S);
}