void main(void){float e,r;int i = 0,symbol=1;printf("input e:\n");sacanf("%f",e);r=0;do{i++;r+=r+symbol/(2*i - 1.0);symbol*=-1;}while(1/(i* 2 - 1.0) >e );r=r*4;printf("pi is:%f\n",r);getch();}
